My guess would be the house isn’t worth $300K let alone $360K.
The owner will have the senior lien on the home.
If it’s a townhome, what’s the rental value of it?
At $1500/month, you’ve basically up-front paid the loan for the next 10 years without interest, with interest, somewhere between 20 years and indefinitely.
The owner no longer has the has any an management costs, no maintenance costs, no mortgage payments, no taxes, no HOAs. If you go to default, he as the $180K to make the loan whole and repossess.