I didn't have strict criteria last year. It was the first year I bought any liens and I just wanted to buy a few cheap ones to learn the process. All 3 were under $1000 each and had decent homes which I figured I could make into rentals. Two were abandoned, 1 was still occupied, but appears to be abandoned now.
I bought some more liens this year with a higher max bid and stricter criteria. I look for properties I could easily turn into a rental and get a desired return on if I get the deed. I actually started looking for occupied homes because I believe there is more likelihood they will not have had all the wiring, pipes, and furnace stolen out of them. If I get possession next year of any of the ones I bought this year, I plan to inspect the properties and then allow the current occupants to apply to rent it from me if the property is in good condition and the occupants seem reasonable. Otherwise it will be cash for keys or eviction.