I answered your question in the other post - but $$ amount invested depends on your personal pocket. Tax liens have something for everyone, from $300 all the way to $3 million. To make it worth your while, you will most likely need to purchase anywhere from 7 - 10 liens at an auction, and focus on properties that are most likely not to redeem. That way if some owners do redeem and pay you back your money, no sweat - at least you get interest (+ penalties depending on your state statute). But, if you get one, or maybe 2 that don't redeem, you can eventually end up owning the property which you can rehab/wholesale/flip etc. For the average small investor, maybe $10 - $20k would be a good amount to get you started. You can even use funds from an IRA/retirement account if you have one.