A white marble look quartz with large gray or taupe veining would be lovely and neutral enough for mass appeal.

Some clients would get fancy and use marble slabs and the like, but that was in high-end homes....

If you want some real answers go out and read case laws in YOUR state, and statues.

Nothing luxury but clean basic apartments with marble top and stainless steel appliances. 

All newly constructed dwellings of four or more units are exempt from Rent Control for 30 years, as per State statue; however the Landlord must also apply for a certificate of exemption in order to verify their exemption status.

I think the law you are referring to is Federal statue 8 U.S.C.A. § 1324, which makes it illegal to harbor or encourage someone to stay here illegally.

Here is what Fair Housing has to say regarding immigration status:"<an image of the Statue of Liberty>Her WelcomeIs Givento EveryNationality -includingYOURS.Housing discrimination against ANYONE based on national origin is a violationof federal and state law.

But I am not putting all my marbles in that basket. 

most likely you can make commerical purpose loans with your own money with out a license.. what you cannot do is any type of owner occ loan.I disagree with you needing to start a company and webstie and all of that.. you will find all the borrowers you need at the REIA meetings... no amount of training can suppliment actual experince.. most folks looking to borrow from someone like you ( private lender) is looking for cheaper money that the local HML charges.. so do some rate shopping and see what your local HML are charging.. in some states its not legal to take points on the loans only the interest.. again check the laws either read your state statues or talk with a good attorney.. there is a lot that can go wrong with rehab loans and you as the lender are the one that will be taking most of the risk. 

I understand there can be a huge spectrum of problems with consequences varying from "can't play a fair game of marbles" to "oh $hit the house is falling down the hill."