Rocket Mortgage (my current lender) quoted me $100,000 for a 20-year loan at a 9% interest rate, resulting in a monthly payment of around $1,000.

They would have been responsible for issuing and recording the mortgage satisfaction after they received payment.

Our customers typically get a 30 year fixed mortgage with a 20-25% down payment.

Refinance offers a lower rate, longer term and a lower payment.

(Tenants not paying on time, keeping track of payments ect..)There isn't just one problem.

Many late payments" is never grounds for eviction. 

You'll want to talk to a local probate attorney to see how much time that could take.If the squatter is not making mortgage payments, you've got perhaps another month or two before the lender begins foreclosure proceedings.In your situation, I would approach the squatter to see inside the property to assess the condition.

Right now my debt is sitting at around 154k (8k outstanding interest payments). 

You could arrange payments with them (eg $1K a month for the next year with interest).

Could you gift the down payment to your mother in law so she can buy it and then transfer title to you when your house is done?