You need to decide what your goals are. The question that you are asking cannot be answered unless you know your specific goals. I will give you some basic advice.
1. You are making a mistake renting to a friend that is doing the maintenance and upkeep. A rental house is like a small business. You are basically paying your friend to run your small business. You are paying him through discounted rent. If it was a small business you would go out of business. Agreed.
2. If market rent is $1,300 per month then you should be getting $1,300 per month. The fact that you are not getting $1,300 per month means that you are incompetent at running a small business. Instead you are running a charity without any of the benefits of running a charity. Your friend performing maintenance is not good enough. What maintenance has he performed? What was the quality? Was it needed? How do you know that it was done? That's the thing though....I have paid $0 in maintenance since 2014. He has repaired the fence, fixed a plumbing leak, installed a new bathroom vent, upgraded all door knobs, etc. on his own dime. He sends pictures to me as he does things and I've visited the property to check things out.
If you want to be a real estate investor then be prepared to make business decisions. If you want to be a hobbyist and play at running a business then save yourself the heart ache and forget about it. If you want to run it as a business then you need to bring it up to market rents. What do your numbers look like at market rent? Around $14,500 a year in mortgage, insurance, taxes, HOA, etc. $15,600 (maybe $16,800 if I'm lucky) a year in potential rental income.
You have ten years left on a 15 year mortgage at 3.125%. You are currently paying more towards principal every month than interest. In ten years this property will be paid off and your cash flow will increase dramatically. I am assuming this used to be a primary residence because of the interest rate. You are not going to get anything close to 3.125% again on an investment property. In real estate terms that is almost as close as you can get to borrowing money for free. That's why I have been hesitant to sell. I'm looking at that cash flow when it's paid off. Also, I've been paying half every two weeks since new, so I'm closer to around 8 years to go. Semantics.
Another option is to try and recast the loan for better cash flow but I don't think that you need to.
Your alternative is to liquidate and buy another property with better cash flow. You are going to pay transaction fees, higher interest, and push a payoff down the road 30 years. You can calculate the NPV of both options fairly easily with an NPV calculator or look up how to calculate NPV. My intuition tells me that your NPV will be better on your current rental if you increase the rent.
Your other alternative is to refinance for 30 years. You will get a higher interest rate with a trade off for how much more in cash flow? You can calculate the NPV on this alternative also.
I would recast or get it to at least break-even and pay it off.
