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.

@Elizabeth KingYour accountant is wrong.

Maybe look at numbers and properties you could do a potential house hack and begin to plot out moves but I don't want you to fall into the analysis paralysis group and never make a move, have people that will encourage and keep you accountable. 

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

I learned how much an escrow account check matters to your overall mortgage payment.

It probably won't come close to $150K.Run the numbers if you put the profits into a savings account paying 5% interest and see how that compares

Many skip tracing companies have a minimum count or spend.

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.

These methods include: Detailed Engineering Cost ApproachDetailed Engineering Cost Estimate ApproachSurvey or Letter ApproachResidual Estimation ApproachSampling or Modeling ApproachExperience or “Rule of Thumb” ApproachIt’s important to understand the differences between the approaches including which one best fits your property and the reliability of each approach.DETAILED ENGINEERING COST APPROACHThis approach compiles the costs from construction and accounting reports to build a report.

Some people love the larger companies and some people prefer the smaller ones.