Thanks for all your responses. Here's some more info:
1) I don't want to be a real estate investor. This was meant to be my "forever" home--it only became a rental because I moved into my spouse's house. If I sold it, I would likely invest in some kind of mixed bond/stock fund.
2) Current financial situation is good. Both of us have good jobs, and this house is the only debt either one of us have. I have decent savings stashed away, but would like to have more. I have a good pension plan at work, but would need additional to retire early. So I could stand the expense if I could be assured this was a good long term investment.
3) I thought of refinancing, but paying longer on the house doesn't appeal to me. And it still doesn't fix the fact that the rent barely pays interest, taxes, maintenance, etc.
4) Floors in the house are original and not very high quality (think linoleum and cheap carpet). I'm thinking whichever way I go, I'm fated to buy new floors once these tenants move out, among other things. Those expenses, plus the normal expenses of selling make me think I'd be lucky to have 50K in hand if I sold.
5) On an emotional level, part of me wants to hold at least until it's back to what I paid for it. But logically, I realize that's not very good thinking. Right now, based on all your comments, I'm leaning toward selling in spring 2019, or when my current tenants move out, whichever comes first.