In order to file the in rem quiet title after a tax sale, you must have three years of active possession counting from the date you were entitled to demand a tax deed, going forward.  

You can pick them up, in rentable condition (or close to it), in okay/decent neighborhoods for $80K-$150K and they will rent for $1400-$2000/month total (many are Section 8, but those are market rates also).More in demand A/B neighborhoods will run the gambut from $200K-$400K, and will rent for $2000-$4000/month total.Rough numbers, of course, but that is about the gist.  

As someone said, inspect and then demand a non-refundable pet deposit.

He can later claim that he did not receive this money from you and demand a second payment - either because he is a crook or because he got drunk/high on your money and forgot he got paid (ask me how I know).

I wouldn't show a place to people at one price and then demand a higher rent based on demand; besides, high demand is a good problem to have, as it lets you be selective of your renters. 

The market to buy homes that have passed "las demandas litigiosas" so can legally and directly be sold to you is a very closed market for the select few.

IF YOU CANNOT AFFORD TO HIRE AN ATTORNEY, YOU MAY BE ELIGIBLE FOR FREE OR LOW-COST LEGAL ASSISTANCE;DEMANDA PARA DESALOJAR ESTA DEMANDA PARA DESALOJAR INVOLUCRA PLAZOS INMEDIATOS.

If I charge my rack rate, I don't need to demand a percentage of the sales price.Back to your problem, I have no doubt you're providing value--there is no way to get compensated the way you want without getting licensed.

It won't take long before you are the expert in your market.You will soon be able to compress all the data: valuation the location, size, property features and market demand as well as other local comparisons pretty quickly with each new tenancy.  

I have to assume there's some kind of increase in demand as the city becomes more and more hip.