Rental assistance varies from program to program, but based on my experience with Section 8 housing and similar/subsidiary programs I'll share this:  the person typically has a "value" associated with their assistance and the program bases that on the market-rate for each property. 

The fund takes ownership usually through a LLC subsidiary.

Using an umbrella S corporation with a subsidiary for each deal is a common way to do this.

This can be an attorney's dream, the operating agreement will be more involved, a trust can be a member of an LLC or an LLC may be in trust, any corporate ego can be an affiliate, subsidiary or controlling entity of another.

Now if you are a massive company with 30 subsidiaries you want to be headquartered in a friendly state.

Having non-liquid assets means pledging the assets, this is not a DIY thing for you to try to do, get a corporate attorney, familiar with subsidiary and affiliate entities.You have a lot of bases to cover in the Operating Agreement, buy-sell agreement, removal of officers/members, pledged assets, accounting of profits, hold harmless between members, insurance loss proceeds, cut-off amounts for disbursing funds and creating liabilities......have your attorney address these as well as other aspects.

There are some Canadian banks that have US subsidiary banks or branches (TD, RBC, BMO) where Canadians can get residential mortgages but usually there are substantial restrictions such as only servicing specific areas of the US, having to own the property in your own name rather than a company name, only applicable for 2nd homes (rather than regular rentals), not applicable for multifamily properties, etc..

Amazon is giving credits to those who use the brokers that work for Amazon subsidiary..

does anyone know if they are a subsidiary of BOA?

It is a fictitious name of a type of entity in which you have multiple subsidiaries of a parent LLC (in the most general of senses).