Set up a bar fridge, hot plate, beds and all essentials and make it clear to everyone that they must not leave the living room except to go out side, You will also need to restrict bathroom use to a single sink, toilet and small shower. 

The HOAs in that area can incredibly restrictive.

Depending on the area there will be restrictions.

If you have an existing loan, there may be prepayment penalties, or some other restriction,  that you need to be aware of. 

As far as the legalities--Round Rock does not currently have an ordinance against STRs like Austin does, however many of the HOA's do have restrictions.

Here is the link for Freddie income limit look up, if the property Is located in a low census area, then there is no income restriction http://www.freddiemac.com/homepossible/eligibility.html

But if you consider the area restrictions and the needed sophistication of the investor it may be considered less ideal for some.

To answer your question about the area or type of property, yes, you can make the agreement more restrictive that way, and it is obviously better to talk this through with the agent before you sign the agreement.

However, if you're not in an HOA (or in an HOA that doesn't restrict STR's - seems hard to find!)

Network with your local investor community and look for an opportunity to invest in a joint venture which would mean fewer restrictions than investing as a Limited Partner.