T...you have come to the right place. Try another tomato website, also. You have challenged yourself a bit by doing seeds instead of plants. Use a light planting mix and keep it damp...you know how to germinate seeds....right? Tomatoes have a few primary "likes". Sun, sun, and more sun is what they want. The foliage Does Not like to be wet/damp. Figure out a support system ahead of time. Containers work well...5 gal or bigger, and a very airy/light planting mix (well-watered and fed). Go for it!

It is TOO LATE starting from seeds in your zone now. I would suggest that you buy plants. It will take a minimum of 6 weeks for what you may want to start now, to become an 8" plant, that you can buy from any nursery now.
I am in a similar zone (as plant out time is concerned) and I started my seeds back ob 27th of February (9 weeks ago) and have already planted some of them.

seysonn is right. Especially for a plant like Mortgage Lifter, last time I planted ML in the garden it was 110 days and still had no ripe tomatoes. I shoot for early May to plant.