Part of what Jim said is true. For SSI, YES any money you have (bank accounts, stocks, bonds...) will be looked at for SSI. You can not have resources above $2000 for a single person, $3000 for a family.
For SSDI, you coud have a million dollars sitting in the bank and still get SSDI if you medically qualify and have enough work credits.
Just saw what else was written, the home you live in does NOT count (rental property does), a car you use for medical purposes does NOT count, if you are married your spouses car does NOT count if they work. Land, unless you are living on it then they DO count it, but if you have a home on acrage, it can't be counted against you. This is all for SSI. As far as SSDI, you could have 20 cars, 3 houses and so on and still get your SSDI.