After paid off would bring in about 10-15K a month in rent and equity of 2 mil today's numbers (hopefully double in those 15 years).  4 rentals in texas 2 out of state.

Can landlord collect double rent or do they owe her a refund?

Take a picture of their driver's license or state ID.

The guest house is set up with a kitchen, bathroom, and then a large living room area that would double as a bedroom.

If they do let them stay for a couple of extra days, do not simply take the current rent and divide by 31, do that and double it.

Monthly mortgage payments including insurance and tax would be around $475 while the rent would be around double that, leaving me with a monthly cash-flow return of about $500. 

You make some good points.Then it seems to me that flying in before making a purchase (for example when you find a property which seems to be a deal) would be enough to scout out the neighbourhood and get a feel for the property - outside of what lives on paper and pictures.

If he is, great, you have s good picture.

You will get the deposit when the transaction settles and you don't want the tenant coming back later saying it was more.Try to get pictures of the property before the tenant moved in to establish move-in condition.

Some of the books I've read paint what seems like a pretty rosy picture, so I appreciate this realistic response.