If you are a higher income earner, keeping it may make more sense. Condos have no land value so you should be able to depreciate your entire purchase price over the 27.5 years, but check with a pro.
Normally my 1% producers (buy for $100k, rent out for $1000/mo) I buy with cash provide me with an ROE of 7%, but those are houses. The big return and reason I would pay all cash is for the equity capture buying quickly at a discount and value add opportunity. Otherwise I'd finance the purchase.
The HOA eats cash-flow, but also provides value. You won't be cleaning gutters, painting your exterior or replacing/fixing your roof, mowing/watering your lawn, removing snow, trimming trees, maintaining the driveway or the deck, pool, etc but I will. I'll also be paying higher insurance premiums as your structure and exterior are covered already.
So, a headache-free 4% return with tax advantages and appreciation potential isn't the end of the world. Condo financing can be tricky, especially as investment property. If good terms are avaialble to pull some cash out I'd consider getting to it while you can. I would not be motivated to sell as long as you have a good tenant.
When you do sell, FSBO and seller financing are options to maximizing price and reduce transaction costs significantly.