In my case, I have residential rentals in one LLC, commercial properties in another, self-storage in a third, and my real estate company operates in a fourth.

In our management company we have cases where section 8 covered 200/m.

I work for a building materials company now and took their online game from Zero to very engaged in the past few years and it's been really fun.

Since the previous owner is getting most of the proceeds does the closing attorney issue him a 1099S and then issue my company one for a much lower amount?

Most PMC's will add extra fees to help the company make some extra revenue.

Could you recommend a trustworthy and cost-effective company for this? 

MF properties are viewed as businesses, thus often priced as a multiple of annual income potential (like any other business, whether you're selling a donut shop or a tech company).

Sadly, on BiggerPockets, some are quick to label companies as scams without real experience.

Looking at this past week's CMI, it's interesting to see the buyer/seller positioning in the SE-ish area compared to the NW-ish area with rates high 6's in JanuaryStill bullish on W/NW future demand due to TSMC factory and other companies (dashboard snapshot below) but time will tell.

With where you are at currently, I would recommend a regular tax prep agent from a company like H&R block.