Not sure about rent since the current owner took possession after a tax sale and have not yet evicted the former tenants. 

They had to cut and remove any surface or areas where bodily waste was found, clean the area with special cleaning liquids, and filter the air with o-zone machines.Some of you may be thinking what about the tenants possession?

I recently bought a duplex and one of the units will be vacant on possession.

When you get possession the plumbing, fixtures and everything will be ripped out.

The "right" way to deal with this is eviction, but with an abandonment if there is nothing of value in the unit, we just retake possession.

Part of the 1031 is you are NOT ALLOWED to take possession of the proceeds of your sale so you have to hire a company to act on your behalf, $$$ 2) You have a limited amount of time to identify and then close on the replacement property or else the initial sale becomes a taxable transaction. 3) Finding a replacement property in that timeframe may force you to overspend $$$ :-( on the next property(s) just to get in done. 4) The tax paid now is less then the associated costs of completing a 1031 and the possible cash out refi. 5) Fear of the unknown.If you want to create wealth for multi-generations you could 1031 all your small investments into one real large one (SFR and duplexes into an apartment complex) then when you pass your heirs will get the asset at its stepped up value (value on the date of your death) and could sell it at that price with no tax owed.

Rental property 4 units all are on month to month and buyer may request that property is vacant as of date they take possession.

Once you have gained lawful possession, it doesn't end (under pre-2020 rules) until the taxpayer redeems. 

On all paperwork the property is under my clients LLC, but he doesn't pay the taxes cause it's actually owned by another company using his name.I know for adverse possession he has to be paying the taxes, but what about a lawsuit or claim to the building?

If Applicant is approved for occupancy, the applicant agrees to sign Landlord’s Lease and take possession of the property.