What are some companies that others are using to insure multi-families of this size?

Here are some indicators to help you assess a buyer's seriousness:Questions: Serious buyers will ask detailed questions about the property, such as maintenance costs, neighborhood amenities, and property taxesStrong Offer: If a buyer makes a strong offer quickly, it often indicates a high level of interest and intent to purchasePrivate Buyers: If approached by a private buyer, ensure they provide a Letter of Intent (LOI) and proof of funds.  

The market has a lot of strong points right now: affordable entry prices, great rent-to-price ratios, and high demand for rentals, especially in the Section 8 space.What’s even more exciting is the direction Detroit is heading.

My client recently purchased a 3/2 single family house for $160k that was near turnkey and already rented at $1900/month and in a very desirable residential neighborhood!

My current portfolio includes two 3-Bed/2-Bath Single Family's in my home state.

Could be their parents or other family  members.

It should be pretty accurate - high level data sites are not always going to be perfect, but should always be directionally correct and AirDNA has a pretty strong track record. 

I am considering offering him $1.8m with a low (or no) down payment and seller financing at a low interest rate so I can at least break even on cash flow after getting rent closer to market value and with upside potential as a MTR and strong  appreciation opportunity.

If the place is vacant, you are still taking that money out of your own pocket.I don't disagree with having a strong cash position; most of my properties are f&c.

It explains the team that you should develop to have a strong foundation under you while investing remotely.https://www.biggerpockets.com/blog/core-four-real-estate-team