Landlord friendly and low property taxes combined with how close it is to CA it makes visiting properties and building a team easier. 

My other option to house hack is Pittsburgh as I have family there but the property taxes are insane and it seems like the room rental market is very college oriented (I could be wrong.)I'd appreciate any feedback on Hagerstown and househacking. 

Using the next ten years and the snowball method to pay them off.

We find that mom and dad are making sure their kid is paying since they're on the hook too. 

For my first property, is it A: better to pay cash and see how it cash flows or always use loans and save money for down payment and other investments?

There are many strategies to investing in real estate, and I won't say any one is better than another, but I think you get what you pay for and no one wakes up in the morning wanting to be a slumlord.

If you need financial help, ask under the "Finance, Tax, and Legal" forum.

He gets an option to buy it for the remaining balance on the mortgage, and pays my mortgage down.Call it rent to own, or call it a loan with free rent as interest plus option to buy.Will it trigger due on sale?

Some states don't allow the landlord to earn interest off the money.From what I can see, Minnesota requires you to pay 1% interest per year to the tenant, so I hope you are complying with that. 

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).