I bought a property through Miami Life Realty to ABC Capital Management with a loan from a company that I am not sure if it even exists, since there are many different companies with same name, but the address does not match anywhere and on the papers i've signed there is not any representative from the lender's company.

Usually the minimum loan amounts are higher compared to a 1-4 program with a loan minimum often of $400K.

I even got an email from a private lender offering a loan AND the collateral due to the borrower burning through capital and now they are stuck with it. 

If I’m going to use a combination of hard money and conventional (maybe FHA) loans, I will need a LLC for hard money eligibility anyways.

As a private lender would you pay the full 100%, or still do 75% Loan to Purchase price and have borrower put money in?

I also have a primary residence with nearly a JUMBO loan at a high interest rate and I own a vacation place in cash (small trailer not worth much money but i also own the land) in a different state that I pay RE taxes on. 

Most banks have restrictions and a Clause where the mortgage/loan becomes "Due on Sale".The biggest benefit of going from personal to LLC is to protect your assets against a law suit due to an injury or death by someone renting or using the property.

I always do new leases, and to Kevin's point I do make minor tweaks most times I do that anyway even if the major purpose is to extend duration.

We have one that offers 10% down and 30-year fixed as a second home loan as well.

As to the second one, they and others (not that long ago) used to advertise fixed-rate loans at 2.4% and 3.6% interest rates.