Let's break it into 2 questions:
1. Does it make sense to keep the house, and
2. Would you get 2nd mortgage.
1. You'll have 90k mortgage, house value 100k, earning 550pm rent.
Your gross rental yield is 6.6%. say you refinance this as a BTL mortgage, you'll be paying 5% interest. So 2k a year to pay property tax, insurance and upkeep. Before income tax.
How secure would the rent be? Based on values, I'm assuming a very rural area. How long would it be vacant between tenants? What if interest rates increase and it's loss making?
Mortgage repayments 1030, so this is going to be cashflow negative, and a major commitment to you. Realistically you would need to refinance it over a longer term to have any chance of getting a mortgage.
It's purely a property price play. Do yoy want your entire assets tied up in property?
2. Mortgage.
What age are you both?
What's your gross salary? Are you both employees?
Any dependents?
You need to pay off the car loan, and refinance the other mortgage over longer term as your monthly commitments are too high.
On, and look beyond PTSB.