I worked under cars up on jack stands for about forty years before finally getting a two post lift, so I feel that I have plenty of experience with your subject.

I would suggest for safety reasons that you don't go too high with jack stands. I also would suggest that you don't try to substitute anything for jack stands. Many people have been killed using wood and concrete blocks.

You might try a set of factory ramps. With a good tall floor jack you can drive one of the car on the ramps, then raise the car with the jack and put a second pair of ramps under the other end. That will work for some things, but not of course, for doing suspension or brake work.

You also might try a set of truck jack stands. They have a larger base to make it safe to support the car higher. The problem then is getting the car up that high.

I hope all this helps and I hope that some day you can end up with a two post lift. You will think that you died and went to Heaven.