Joel has some valid points but, if you start talking about foreclosure rescue, you might want to check with the laws of your state regarding licensure requirements as a foreclosure consultant.

I do run credit & background checks that they pay for, but that is separate from just the application.

Positive landlord references No evictions Cash available for security deposit and first month’s rentNo Pets allowedSublease and sharing, airbnb not allowed,Reusable tenant screening not allowedEvidence of responsible character … i.e. reference letters, follows instructions, no lying, shows up on time, no major criminal record.

Start checking Zillow, Redfin, etc., for both rentals and sales prices. 

a lot... a ton.... off the charts.... not even close...Check real comps in area

A contractor can help yes when it comes to looking at it and telling you how much or what you be looking at if you want to upgrade or fix something visible but you need the inspector to check out the roof AC and plumbing thoroughly despite what it looks like in person I’ve seen mini jacked up ceilings.

I'm a licensed realtor so I have access to the local LMS, I check out public LMS sites, Facebook, Craigslist, and the few deals I find are gone far too quickly...I work a full time job and do real estate on the side.

If you go the new home route, check the rules on resale and if there is a right for the builder to purchase it from you or a minimum time before you can sell it. 

If Airbnb has confirmed these are Service Animals I wouldn't make any waves and see if there are any issues after they check out. 

check your local laws as a few people on BP have posted that you can only do evictions for unpaid rent in some areas.