He was pay ed to install a AC unit in my home and disappeared  he refuse to answer the phone calls texted massages he stole my money and won't respond 

You can compromise without loosing good paying tenants if they pay on time. 

Of course the tenant doesn't want to pay, she's got a free ride.

How much do they want you to to pay, to pay off one of the mortgages (or both of their existing mortgages)? 

For example, a buyer putting 20% down on a $500k home would pay around $500k in interest over the 30-year life of a typical mortgage at a rate around 6.5%.

We typically pay somewhere in the range of $3500 for a new, basic furnance, including install, if there are no other modifications to the system required.  

I know that is a long pay back period but don't plan on selling anytime soon, plus you never know what nat gas prices will do. 

Additionally, the supply of homes for sale is constrained because of this and will be for some time putting upward pressure on prices in most markets.Thinking about renting your house in Seattle would be wise as someone else will pay the mortgage down, and rents and the value of the property will go up over time.

After holding a property for more than 10 years, investors can sell the property without having to pay capital gains tax on the profits, making it a favorable environment for long-term investors.Investment Strategies for American Investors in Germany1.

If it has any basis at all (such as you left the apartment during your lease term for what you felt was a justifiable reason and stopped paying rent, but the landlord disagreed) then you may be better off paying a rather small settlement.