I would use the 20K as a down payment on an FHA loan to buy a 2-4 unit property. Negotiate that the seller pays your closing costs, so that the full amount of the 20K can be used for the down payment if it is needed? You will live in one unit as owner occupied for a min. of 1 year before you can rent that unit out, and then you will collect rents on the other units. With 20K, you will be able to get a purchase of up to $571,428.00 or $571,428 X 3.5% = 20,000.
So go shopping to see if you can get a decent 1-4 unit at that price range or lower. Look to see what the rents are that are coming in off that property? The more rents, the more potential cash flow. Do a cash flow analysis on the property using the BP calculators. If you find a decent property, put it under contract and close on it as an owner occupied FHA purchase. Use the cash flow to build a nice nest egg to rinse and repeat down the road to another property. Keep building you portfolio that way.
Eventually you have enough passive income coming in that you can choose to keep working or live off part of your cash flows and invest the rest?