We paid a contractor to do it with landscaping timbers. They did a good job at a reasonable price.
Depending on what kind of terracing you are contemplating depends on whether you can do it over many years. The system we put in really had to be done all in one project and the situation was too urgent to do it any other way since the corner of the building was near the edge of the failing slope.

I started with a modest ranch home on a sloped lot. As seen in the graphic below the drop was about 14 ft from the high corner to the back. Just steep enough that most all of the lot was unsuitable for any use.

The retaining walls are shown in blue. The walls on the right and in back are now complete. I still have the ones on the left to do.

The right front corner has a large flat flower bed that tapers to 4 ft and steps down in places as it runs to the rear. This wall plus the cross wall from the back house corner creates a large flat for parking or a future garage addition.

From the parking, it drops 4.5 ft to the grass patio that is one step below the small existing concrete patio. Steps lead down to a lower level and a grass ramp was left along the property line for mower and wheelbarrow access to this level.

The walls are poured in place concrete. All of the form material was designed from common items found at local big box stores.

I looked at using the popular blocks now being sold, but to get the wall height I needed required blocks too heavy for an old guy to handle. This project is not going real fast. My construction crew consists of one guy nearing retirement age .... me.

If you're going to do it yourself and it will be a long-term, ongoing project--word of advice. Start from the BOTTOM and work up. Been there, done that.

-Ron-

Pls8xx,
Nice graphics. Impressive that you did the work yourself.

Yep, I did it myself, and soon I will be happy to post pictures....but my back lot is sloped about 45 degrees and solid mountain, with empty spaces here and there, and rocks galore, no cleared ground anywhere. I started by pulling weeds by hand for two full years, to uncover the actual slope and shape, and to see where the rock was jutting out and where it wasn't; which trees/bushes were trash, etc. Sweeping the rocks was very Zen, but it also helped me see the hollows and I swept clean what was clearly no good for flatness. Then I started to see the slope divided naturally, and where it looked like there was space to make a straight, horizontal line, we found the biggest rocks and lined them up to make a rough terrace, as much as possible in line with the shape of the mountain itself. Start from the bottom, absolutely!!!! You now have an area above the terrace with a potential flat space. Then take out by hand all of the medium (around fist-sized) and small rocks above the terrace, and lay them in a path under the line of terrace. I promise to upload a picture this week. The next step was to take dirt from under the trees that had been sitting there for years (forest duff, I belive it's called) and fill in the area above the terrace, to create a flat space of dirt to plant in. You are filling in a space with a sloped bottom, but as you put the dirt in, more on the bottom, less on the top, it becomes flat. Sometimes these spaces are only a square meter, sometimes more. Nothing holds these little walls together, just well placed rocks, but if you want or to need to you can put cement around them. Depending on the size of your rocks, the wall will be one layer high, or two, but they shouldn't be more than 50-60 cm (sorry I think in centimeters as I live in Israel and the inch thing has gone from my head). Dig that ground, now a flat space above a little wall of terrace, making sure it is rock free and add enough dirt to be about a foot deep. On my slope, anything deeper than a foot is luxury, under which is solid mountain. Basically, you are hauling rocks to make horizontal walls on a vertical slope, filling in the dirt above the wall, and using the misplaced rocks to create a path below the wall. The pictures will make it easier to understand. I also have put old tires here and there on parts of the rock to make planters where it's not big enough to carve out a regular planting space. We had no contractors, gardeners or other help, and it has taken 6 years to get where I am now, but it's lovely and I did it with my own two hands (with DG, who discovered she loved gardening!). Batya

Can't wait for the photos!
Ron did you start from the top? I have no choice but to start at the top.. Cherry

If you absolutely must start at the top, I guess the important thing is to clear a small area as well as you can before deciding where to put your first terrace. Other comments that those trash trees and all the rest growing there is what's keeping it all from eroding straight into your living room sounds right on. Pulling weeds and random growing things to get a sense of the actual slope and what's under it is vital (jutting, non-moveable boulders, for instance) but leave the trees until you can see clear ground around them. Is there a non-rainy season, where you can have 2-3 weeks with no rain? (Around here we have 8 months with no rain, so there were no worries about mudslides!) Maybe sowing oats or rye on the places you clear would be good, as you can use it for green manure when you cut it, and it will hold whatever soil is under there until your next step. I'm working on the photo technology, keep fingers crossed! Batya

I have never heard of a landslide in my area but i guess if the conditions are right it could happen anywhere.

My plan for my Sandy soil 70 degree drop off at the edge of my yard that is 107 feet wide, is like this..

Work in small managable sections
Add as much rock/ junk concrete as I can find in the form of small walls and just tossed to the bottom of the hill.

Add organic matter in the form of leaves, coffee grinds and old curb plants (free and abundant) to the surface of the the soil

Remove all junk trees and grape/ivy vines.

Plant tall native grass, native flowers and low trees that have open canopies to allow light to get to the soil surface.

Don't get discouraged and be persistent.. this all will take years...

I have no money for this project everything needs to be done for little or no cost by me.

I recently picked up from Freecycle blue slates, and had a yard of dirt from a construction site delivered free. The dirt seemed so big in the driveway but once it hit the hill it disappeared real fast.

My DH has Crohn's disease and often does not have the energy to help. I have to have enough energy for the two of us.

Keep my eye on the prize, a beautiful landscape that my DH will be able to sit outside and enjoy.
Cherry

You already found out that the prior neglect by the prior owner of your property was not helping so doing something will almost certainly create a big improvement.

I have just finished terracing the steep hill at the back of my house in Spain. I started at the bottom with winding paths cut into the hill side with 4 inch concrete mortar into which I have placed stone slabs recovered from local fields. The sides of the paths are supported by drystone walls which lean into the hill. The land in between the paths is planted up with various shrubs which keep the soil in place. Above these are three 30 foot concrete block walls dressed in stone also set onto concrete footings. The dug out soil is used to create raised soil paths in front of the walls for extra support. In between the terraces are pine and almond trees planted for soil retention and drought resistability. As yet I have no photos but plenty of blisters instead.