There is no reason to spend money on existing tenants. 

The pay or quit notice will assist the tenant in getting her handlers moving.If your tenant is lying, which is always a possibility, regarding the employment being temporary moving quickly will save you time and money in the event you end up having to evict as well.Issue the notice.In regards to accepting partial payment...read your state specific landlord tennat regulations. 

My wife and I want to purchase the property, continue to rent the four existing units while the 5th unit is being renovated, and then move into the renovated unit ourselves.

I sold 6 of them to capture 3% of the entire market, and I think that was 4 more than anyone else sold.I would venture to guess that the entire amount that even exist in Anne Arundel county is maybe 50 properties.

So the IRC regulates how the home is to be built then the IPMC regulates how the home is to be maintained.

There is ANOTHER petition circulating that will confiscate the permit of any property that doesn't generate enough Occupancy Tax in a year.https://www.tahoedailytribune.com/news/petition-seeks-to-tighten-south-lake-tahoe-vhr-regulations-maintain-current-cap/

Quick question for you: are there any regulations on using AirBnb with an FHA loan?

We have not had it inspected  by an engineer yet but I feel pretty confident that all we will have to do is bond the existing piers  because they are dry stacked and not mortared. 

Obviously regulations in the US are much less complicated, taxes lower, laws much more landlord-friendly and profit margins higher than in Germany.

With any luck and a little discussion you might be able to find As for using Legal Zoom versus a local Attorney, I would recommend finding a competent local Real Estate Attorney as they know the in's and out's of the State and Local laws and regulations that apply to the area in which you are working.