Further to the point above by @Jeff Cagle, California's almost-mandatory disclosure, the Real Estate Transfer Disclosure Statement, asks the seller in C.12. to disclose whether there are "neighborhood noise problems or other nuisances." 

The city has sent a letter to me stating that the weeds are a nuisance and need to be removed by 10/12.

I’ve owned one rental condo in close proximity to the oceanfront area that is generating decent passive income; but the HOA’s and board have honestly been a nuisance.

If we're talking just about asset protection and assuming you're doing your part, insurance prevents nuisance lawsuits.

I would make sure you get a propr mgmt certification to make sure you know EVERYTHING about service dogs, marijuana laws, eviction info, how to handle all tenant issues, like them vacating before their lease is over, tenants not paying rent or causing a neighborhood nuisance, etc. 

If possible find someone who has worked with RE Brokers before and understands the nuisances of the industry. 

I started with little, in the beginning did more of the nuisance work.

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. 

However, (a) there are IRA/401k compliance concepts that you should be aware of and (b) you should develop an efficient method for accessing IRA capital - I'll often get introduced to syndicators that find dealing with IRA/401k money to be a huge nuisance, which it does not have to be.On most syndicated deals there will be leverage involved, resulting - potentially - in taxable UDFI to IRA investors.

If N is merely claiming $200, better to just pay or offer half and ask him to notify you *before* there is damage.Or pay a lawyer to defend a nuisance suit for damages...