Mentioned also, if it's in a bad area I will add an alarm system along with wrapping the outside unit to always be on with a loud exterior siren if ever disturbed.

Runaway, disturbance, harrassment, civil matter.It's a street full of these duplexes.

I would NEVER disturb a near 100 yer old foundation unless replacing it.

Any other buyer will need time to do DD and may end up backing out like I did... so maybe they will just come down and be done with it so they don't have to disturb the tenants more than necessary.

Yes, also to disturb tenants less by working above them.Maybe you could gut the whole building first, so that your plumber and HVAC guys could get those systems done first, then do the finish work one unit at a time.

BUYER IS NOT TO DISTURB OCCUPANTS.

Tenant and guests or invitees will not use the premises or adjacent areas in such a way as to: (1) violate any law or ordinance, including laws prohibiting the use, possession, or sale of illegal drugs: (2) commit waste (severe property damage); or (3) create a nuisance by annoying, disturbing, inconveniencing, or interfering with the quiet enjoyment and peace and quiet of any other tenant or nearby resident.

.- And here's an excerpt from the actual Washington state law (RCW 46.55.070) that authorizes it (read the bold part in subsection (2) about residential property):RCW 46.55.070Posting requirements—Exception.(1) No person may impound, tow, or otherwise disturb any unauthorized vehicle standing on nonresidential private property or in a public parking facility for less than twenty-four hours unless a sign is posted near each entrance and on the property in a clearly conspicuous and visible location to all who park on such property that clearly indicates:(a) The times a vehicle may be impounded as an unauthorized vehicle; and(b) The name, telephone number, and address of the towing firm where the vehicle may be redeemed.(2) The requirements of subsection (1) of this section do not apply to residential property.

So all my friend has to do when a tenant causes problems (drugs, disturbing other tenants, etc.) he simply tells that tenant he's going to file eviction papers over the back due rent and the tenant moves willingly and he never actually has to evict.

I rent the other side to a tenant a little under market value for the peace of mind that he does not disturb me and takes care of my property.