.), so I'm targeting fractional interests in 50+ door properties for my investments.Also, it's noteworthy that quadplexes and below are valued based on comps, vs. 5+ unit multifamily based on cap rates.

I'd begin checking them out with the state finance department in the state they are organized in.Also, beware of investing in a note with other investors, taking a fractionalized interest, there are many out there in the note business that know more about marketing a product than they do the product, you'll find overstated valuations of collateral to minimize the LTV implying a margin of safety and saying everyone is covered, that may not be the case as I've never seen a dollar split 3 ways evenly.

That is, do I want to buy the notes whole, participate in a fractionalized note (if legal in your state), or invest in a mortgage pool?

Welcome to fractional reserve banking.So they pay you 10c interest per month but collect $5 per month in interest on the loan.

They will only pay a fraction of what they pay for your avoided usage, but they WILL buy it, it is required by law.I will exclude Mexico from this discussion because I have no idea nor care what goes on there.

It's a fraction of the cost of these 'gurus' and you actually get an education without an agenda. 

or fraction notes?  

The used appliances I buy are in good condition, look good, and cost a fraction of the cost of new.  

Will you be taking on investors and using their money to fund loans (i.e. arrange the loan and make a fee), arrange fractionalized loans, hypothecate loans you’ve made, perhaps start a mortgage pool, loan your own money, broker NPN's, or some other strategy?

You can analyze properties and run comps in a fraction of the time it takes trudging through the mls comps.