Once I start as an agent, I will be actively learning the market in general and for my own future purchase of a rental property.

Also, longer-term, the net proceeds from this deal will fund future deals and better cost of funds on those deals, which done right will help me continue to beat 401k returns. 

I recently listed a property in Haverhill with a HUGE upside on the cashflow potential,  future value add potential.

The construction is more likely to be hit and miss, resulting in nearly every street having at least one house under construction for the foreseeable future.

Will anyone even think about lending me money for more real estate in the near future, even if I have 20% down? 

will it impact my ability to make future loans ?

@Adam Schneider is right, we can't possibly advise you without seeing the numbers...My gut reaction is keep it and pull the equity out to use on future investments, but that's because personally I rarely sell any of my rentals.

I have aspirations to be a part time real estate investor, mostly for passive income, but I am not opposed to potentially making it a full-time endeavor sometime in the future.

Bearing in mind that I have an additional expense of a property manager, I've been in the "get rich slow" camp, looking more towards the future. 

Look for someone who wants to do the site work, then sell the lots to the future homeowner who wants to custom build and design their own home.