Hold contract, or sell conventional, 4Plex

We have a 4plex, in a desirable neighborhood, appraised at $500k, with rents at $825 (low for the area). Owe $350k. Also, a 1031 exchange, from another property (approx. $30K, used as down pmt). We have taken approx $225 over the last 18 years, in equity loans. Once the Cap Gains are paid, likely won’t have but $50k, if that, left. Would I do better FSBO, and hold the contract? If so, or not, please help me understand.
Thank you,