Be sure to check the unknowns, roof age, hvac, plumbing.

@Solomon Morris greetings,Consider the age of the ductwork itself as well.

No need to get tangled up with someone who will have access to your pocket book and with whom you could potentially produce another living human being that would require time, energy and money.If you do this one step, you'll already be ahead of 50% of my tenants who got preggers/had kids out of wedlock and are now single parents trying to make it on a GED and a $10/hour retail job.P.S. 

So basically, "back of napkin" to see if it loosely works...making an offer, if offer is accepted, during the due diligence, find out the age of everything...re-run the exact numbers and then make adjustments accordingly.  

Do a little market research around the neighborhood to find out rental rates for various properties and how rents differ based on age, condition, parking, neighbors, amenities, view, etc. 

For supply, the Northeast and Rhode Island is still somewhat constrained in my opinion, as there's a good amount of anti-development sentiment here (and elsewhere of course, California is also notably horrible).

5) is there an age limit for you to be able to rent it out?

In quite a few different ways, but the age and repairs needed were the heavy price movers.

Life, Real Estate, stocks, world views, love and marriage, youth and older age. 

Depending on the sqft, and any specifics about the age of the infrastructure, I would imagine you wont be too far off no matter what you find.