Prepayment penalties- usually 1-5 year terms.

@Nathan Gesner Hey there I usually collect the money upfront after I get the lease signed.

First deal does not have to be a home run, a base hit is what I've usually aimed for and thats how I got started with condos and single family homes and as those properties appreciated over time I utilized the equity to purchase multifamily properties that I could not initially afford.Cheers

Having some extra cash reserves over the next year or so, would be prudent IMO. 

By leasing extra space, making a mortgage payment, and gradually increasing equity, it can help defray housing costs.

in many markets you have to go OFFmarket to find the deals that cashflow. the MLS can be picked-over. this is obviously more work. there are markets that cashflow just fine even the picked-over properties. single-family is also USUALLY going to cashflow way less per unit vs multi, with LTRs. 

As for charging extra rent, check with state local landlord tenant laws as could be violating fair housing if charging more just because more members in family.

I think that's fair, but I do feel like, eventually, buyers will start to see the value, and if the seller is willing to go through the extra trouble, they should be compensated.

I'm located in AZ  It is usually about $1 mil.

The great part of buying in the city market right now is that it is mostly a buyers market, and you can usually negotiate good terms.