Glad to hear people are digging in on the neighborhood, my portion (Glendale Blvd and Alvarado) certainly has room to improve...  

If there's a part of the house you don't want to give them access, spell it out in the lease.

Do you have access to the land records to pull docs?

@Jonathan Morning yes almost any financial institution will have access to all the FHA loans.

If he has been doing this for 10 years and you have allowed it with no formal, written reprimand and request to not make material changes and improvements then you are not going to be able to use that argument in court and if you do you should be ashamed.

The land and all the improvements to the land such as utilities, streets, etc.

A self-directed retirement plan (IRA or 401k based) is still a retirement plan with all the same rules about access. 

I have recently got my license in order to access MLS as well as educate myslef.

I have MLS access and I look at REO's and auctions regularly but I have to admit i am stuck.

I specialize in low income housing around South Phoenix, so if I wanted to build a 3000/sqft fourplex I was looking at $300k(Plus other costs) for a building that would bring in maybe $500/month before maintenance costs.If you have access to people who can see a development project all the through, where it actually brings in decent cashflow let me know.Good Luck