If so, would I need to look at the local laws on how much notice I need to give them to move out so I can move in?

You may also have limits on how much you can charge.Again, it's very important for you to read the law.

I would avoid any in DC itself because they will be expensive and the landlord-tenant laws are very, very tenant friendly. 

@Angel SanchezThe s-Corp requires filing for articles of incorporation and corporate by-laws.  

My mom in law is currently in such a situation.

I would contact Jeff Charlow of Charlow Law in Towson or Scott TInney of Cohen and Foreman on St Paul st in Baltimore. 

California is sort of its own beast when it comes to taxes and laws, much more complex than the vast majority of other states. 

Been looking at a little house with a "mother in law cottage." 

I got into a partnership with a friend while in law school and it helped pay for my education, but at the end of it I realized how fortunate I was with a good partner and solid investment.

Underwriter took the position that it looked like dad-in-law might be dummying up paystubs (or giving him a giant and real, but temporary, pay increase) to get his daughter and her husband out of the basement, and refused to use anything but the lower number that was on tax returns for husband's income calculation.