I have one of these and it is pretty decent quality for the price. Can be taken down and put up in about 15 minutes.

Here is a link that might be useful: GH

I have the bigger version of this as well. It is better quality than the other one I mentioned but much more of a pain to put up and take down.

Here is a link that might be useful: greenhouse

Thanks for the info that 10x10 looks like a good solution for less than $200, does it have the ability to run a power cord for a heater?

I run a power cord under the bottom and use a 1500 watt oil filled heater. I may buy a fan powered heater instead this year because they seem to draw less power. I won't run the oil filled on high because the extension cords get too hot and I worry about a fire. Keeping them on medium seems much safer and the GH still stays warm enough.

1500 watt oil filled heater..........I may buy a fan powered heater

Good heater for a "fabric" greenhouse because no really hot surfaces on an oil heater. No exposed heating element. You can buy a heavy duty extension cord that won't heat up.... or run two extension cords out to the greenhouse and join them up to feed into the oil filled heater.

All electric heaters put out heat that is counted in wattage. A fan in the heater will not put out any more heat but might spread it around better. You could do that with your own separate 7" fan

I tried buying heavy duty extension cords last season. That helped keep the cords cooler, but then the outlets overheated and actually started melting. Now I only run one heat source per outlet and only run the heater on medium which I believe is 1000 watts. Haven't had any issues since then.

so which is more suitable for a portable GH? Oil filled, electric or just any heater with fan?

Also, what do i need to get to set the heater to only turn on when the temp drop to a certain degree and turns off automatically when the temp increase to certain degree?

I plan to use those electric ceramic fan type heaters. I have 2 and they seem to put out plenty of heat.

You would need a thermostat for that. Ranco makes one that can handle 1500 watts. I use a few to control the temps in my reptile cages. They cost around $100 though.

After measuring my space and reviewing features I decided on this greenhouse, now to see if it stacks up:

http://www.google.com/products/catalog?hl=en&q=flowerhouse+farmhouse+greenhouse&gs_upl=0l0l1l360l0l0l0l0l0l0l0l0ll0l0&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1366&bih=596&um=1&ie=UTF-8&tbm=shop&cid=11305525256947437879&sa=X&ei=FyLRTtjWJfTIsQKwhqTxDg&ved=0CHgQ8wIwAg