Cons include the two restrictions on amount you can take out (with traditional cash-out, you can do 75% LTV, and upfront outlay doesn't matter), and also that you have to be able to trace back the source of the funds used for purchase as YOUR cash.  

I have found information via truepeoplesearch .com you can also find associated people and maybe contact them thru them.Cole realty source find them on Facebook.

No one can directly provide the one answer, that has to come from the source and through trail and error.

This also manifests on these very forums, the "I'm buying a house, but my loan is being jammed up by X, Y, and Z," threads, where X, Y, and Z, are things that only come up on purchase transactions (income/DTI issues, down payment sourcing, title issues, for example), not refinances ("if they qualified when they got the purchase mortgage and didn't get fired, they're qualified now because the rate/payment is lower, so no need to check income/DTI upfront," no down payments on refis so no need to verify funds / bank statements, no title changes on typical refis, no purchase contracts on refis, you get the idea). 

How would a list source identify a motivated seller with the exception of homeowners going into foreclosure, or someone on their death bed with no heirs.The best lists for foreclosures are auction.com and propertyradar.com.

The best (and least time-consuming) sources for us have been cold-calling & email campaigns.

Anyone know any sources of information I could get on this subject?

Also, look into Green Bonds or Green loans if you are adding EV charging or solar etc. as Banks like to access that source of money if you're modernizing a building to be Energy efficient or leed compliant.

Propstream is a great source to find off market multi's in your area and you can mail or skip trace the owners to see if they want to sell.

Next, your realtor or PM should be able and willing to provide projections on the property, using a reliable software or other source.