I encounter this semi often as I broker to buyers and also own a PM company so often have to do the same or similar transition as you are looking for, for my clients. 

My company provides a comprehensive A-to-Z solution tailored to our clients' needs.

Personal loans through the credit card companies can be approved and fund very quickly and my best rate is 7.9% so shop around as some are much higher.

HELOCs are not available because they are residential loans guaranteed by individuals and what you seek is a type of commercial loan or credit line which are available to seasoned companies with proven financial track record.

The companies that market themselves as "garage door companies" (residential) also almost always do commercial stuff as well, such as what you are looking at.

After reading Brandon and Brian's book, The Multifamily Millionaire, Volume II: Create Generational Wealth by Investing in Large Multifamily Real Estate, I'm a bit puzzled as to if the GP's must have real estate experience, or if someone can connect enough professionals/companies on their team to execute successful investments.

Waivo is an example of such company.

and I was just one little mortgage guy with 450 loans out.. can you imagine the banks with hundreds of thousands of loans and servicing companies.. so having mass equity or paid for keeps this from ever being an issue. then when I sold these off.. most for cash but a lot I did a 30 to 60 month ZERO interest deal on.... and boy you should have heard the cash flow cool laid drinkers..

Many skip tracing companies have a minimum count or spend.

Or does one need a special license / need to open a company?