Use such credit as a tool though, not as a crutch. 

Experts in that area will know, but the internet is a huge tool.

He's an agent with RE/MAX, one of the largest franchises with a great training program and a lot of tools for their agents to use and build a successful business.

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

Let's look at your example of a roofer, assuming he owns the company.He has to pay for employees- they still get paid, even if they are not giving 100% effort.He has to pay his workers to go back for warranty work - effectively paying them to do the same job twice.He has to pay for equipment, even when it's not being used 100% of the time.- but the company he bought it from still gets paid.He has to pay for advertising, whether it works or not.- but the advertising company still gets paid.He has to pay for accounting services, payroll services, tax services, legal services, etc.- they all get paid whether he makes money or not.So, what's your point?

I believe in this so strongly that I have even once confronted a large advertising client about this issue when I discovered they had language to this effect in their terms of use in the past, and asked them to change their policy, at risk of material revenue loss to our company.

You can get the Bigger Pockets paid membership and use their Find a Market Tool to analyze.

Don't know how to analyze a deal effectively?

Effectively offering more than 100% financing.  

Your referencing effective age vs chronological age.