As for 1.5 years vs 2 years of employment you can either have a family member or someone co-sign, as it sounds like you're very responsible and you may have friends or family willing to vouch for you.

As it turns out the parents would not co-sign.

You certainly can avoid these expenses by just paying the seller directly and having the seller sign a "Quit Claim" deed but you run the risk of incurring any liens or other encumbrances on the property. 

I'd typically just send them another year long lease, running from April 2018 to April 2019 to sign with all their names on it, but then that'd lock Person C into staying all year. 

There are a lot of deadlines to hit with exchanges too, so best to have some back up properties selected for what you will be exchanging into.

Moreover, I’ll need to add appropriate language to this effect in the new lease to soon be signed.

@Alexis Miller usually banks require you to sign a mold disclosure before entering if it is that bad.

It should be filled out and signed by the Landlord and Tenant.2.

Would also be curious how you selected those four markets.  

Why not tell him you'll do it if he signs a year lease at market rate to reflect the new condition of the unit.