But I'm almost positive you can not charge by the person like happens with pet rent and what not.

If it's OK, you might keep it accept pets for extra rent. 

That was my second investment property and it taught me about the livable condition rules for conventional loans.Putting in trashed, pet damaged carpeting to get a loan approval?

We also bought a little old lady house that smelled of mold (washer leak) pet urine and smoke.

That same day, after eating a snagged apple from a friend's lunch tray and a sample piece of bread from the bakery next to my university, I headed over to the computer lab and put an ad on Craigslist to become a house-sitter/pet sitter.

smoking and pets just are not worth the hassle IMO

Nicer units don't command as much of a premium as they may in other places, but you can certainly get an extra $100-$200/mo if you allow pets locally, as almost no one does.

The landlord sets the rent (using the market as a guide), the landlord selects the tenant, the landlord selects the lease, the landlord chooses who will do a repair (even if it is the tenant), the landlord decides whether or not pets are allowed, openly or tacitly, the landlord decides whether to have a monthly or yearly agreement, the landlord decides when to replace the carpet, the landlord decides on whether or not to provide appliances (again using the market as a guide), I could go on and on, but the key point is that the landlord is making the vast majority of key decisions.  

Nice couple with 2 kids and no pets.

.)- Down payment: 12k- Rent: $825/month (I allow pets)- PM fee: $123- MX: $82/month (10%)- Vacancies: $82/month (10%...It’s actually been closer to 7% the last 5 years)- Reserves: $41/month (5%...I probably can drop this due to this property being a condo.