Althought 20 acres is not much land it can be improved for wildlife. If you are limited on funds you could try to improve the native vegetation that is already there. One of the most important things people overlook; especially with small properties is placement. You should place any improvements so that you can hunt them with out disturbing the deer's pattern.

If you really want to plant a food plot then cut the trees yourself to save money and hire someone with a bulldozer to clear the stumps. Also, what other foods are available on your neighbors property? If there are big agricultural fields nearby you may be wasting your time with a small field of your own.