Think of it as a bonus room with a bathroom, no kitchen.

A bonus for paying early.

Local is a bonus, not a requirement.

An added component to think about is the forced appreciation/ARV of the home, this "bonus value" will be calculated into the refinance when you do decide to. 

Send them birthday gifts, Christmas gifts, give them a bonus.

You can significantly reduce your taxes with a cost segregation study and bonus depreciation by accelerating your depreciation.

It's always a bonus if you allow pets because people traveling for work very often have pets with them and have a hard time finding accommodations so you can charge a little more, plus collect a pet deposit.

Could someone recommend an engineer or a company that does cost/bonus segregation on a single family home in Center City Philadelphia? 

Also if you have multiple units I send out an email blitz to all my tenants that I have a vacant unit located at XYZ Property and that I pay a $100 referral bonus if someone they refer to me ends up renting it from me.

Ive been telling my clients and myself that when interest rates are at decades highs its hard to cashflow in many markets but if you can refi in a year or so your cash flow will return plus you may be able to take advantage of the 100% or 80% bonus depreciation in the meantime.