@Russell Brazil, I do believe the South Carolina contract is similar in that a clear CL-100 inspection is expected at closing, even if there is an HOA, but if not the buyer only has the following 3 options:Accept the Property in its present condition, Negotiate with the Seller for the payment of these repairs and treatment, or Terminate this Contract by Delivering Notice of Termination to the SellerWe have been clear that we won't be replacing the sheathing as we are not authorized to remove the siding to do so, but they haven't given notice on any of the above options. 

If ONE unit is vacant and both units are equal in rooms/bathroom composition, then the new owner will need to move into the vacant unit and then the owner can either evict to take the occupied property completely off the rental market (5 years off the rental market), evict to take back the occupied unit for personal use like moving in immediate family (2  years off the rental market), or they can evict given the tenant is a nuisance or conducting illegal activity (this is a harder method to evict since you have to provide evidence and have a case but if they're selling drugs and you have video footage or something, then make your moves) and there are a few other reasons for at-fault evictions. 

A long-time resident at where I'm now living told me when a previous owner (that went bankrupt) started accepting HUD tenants, "that's when the drugs came in" (I wasn't living here then to be able to confirm this assertion, but I have no reason to doubt it).The same reaction happens in business ("street fighting" and "lifeboat ethics").

Now, for 1031's, whether you traded up, or down, for tax treatment, your replacement property becomes two for tax purposes.In cases where you traded up, and took on a larger mortgage, the tax treatment is easier to explain and calculate.

I obviously don’t condone drug use in the house and don’t want him scaring away prospective buyers.

but I will take a guess at what your askingif the developer is going to bust this into lots and you stay in you just lost your tax advantages and will be deemed a dealer at the highest tax rates.sell now no risk.. and best tax treatment you could 1031.if its one property and your saying should I partner and they are going to build an apartment on it and we will keep it.. that's different.. but you lose control because your now going to put a massive amount of debt on it.. all though in your area not too risky given market conditions.. and really depends on your developer  known, reputable and stable ?

I was the kid in high school getting offers from private colleges over how high my test scores were, and I ended up ruining so much with drugs, toxic emotions and bad decisions. 

Is it a place where people are making very little money and have none left over, or is it a place where there are open air drug deals during the day and cars broken into every night? 

In these you are purchasing ownership of a company or entity that owns real estate and not the real estate itself.However there is a hierarchy of real estate ownership that complies with 1031 treatment and runs the range from active to passive.  

Whatever you decide to do, you may want to have a documented business process for accepting, reviewing and approving applications then issuing leases that you follow so that you provide the same treatment to all - Then of course you have to stick to this process.