What are some things to be aware of doing tax liens?

I'm aware of them all.

I completely understand that concern and glad you both raised that point about a nursing home, however, I do have a big house and we have casually talked about moving her in with me when that time comes.

I like Finding & Funding Great Deals; Buy, Rehab, Rent, Refinance, Repeat and Raising Private Capital.

Without accounting for management fees (I have not yet decided if I will try to self manage), and with planning to raise rents to typical market of $825 for each of the smaller units, and $1200 for the larger unit, does this seem like a worthy first investment? 

You will also need to determine how much you want to raise.

Let's talk to see if Milwaukee, WI and Raise the Standard Real Estate is a right fit for your goals.Beleza 

Detroit is a great city to invest in one just has to be aware that is is a block by block city and to be careful

If you do the math, since your borrower is paying interest on interest, it raises your effective interest rate by about a point.

Maybe also consider if they are "good people" that work in the community and just want a safe place to raise their family.