If this isn't required, then most likely having the GC sign a completion guarantee to ensure the project gets finished and lender is not stuck with a partially complete asset is the case. 

Seller of said property is not willing to do terms.I go forth into the MLS or elsewhere and find a seller on any type of property willing to do the terms I want AND is ok with me selling their property and substitute the collateral with another real estate asset of same/more value.

Reason is a Heloc generally carries a higher rate on a shorter term and "Can Never" be used as an "Asset, or for PITI reserves" which are both required when you buy an investment property. 

It may not appear this way on the surface but you are going to come out ahead by focusing on purchasing fewer but quality assets rather than becoming a door accumulator.

Look at all the above and more.History, experience, assets, ability to pay, collateral, references, credit score, etc.The more the better. 

Never invest in Longterm assets with short term debt.  

For long term, the main benefit is having someone else pay off the mortgage on an asset while you collect cash flow.

.- long term: there is a shortage of properties in almost all cities and in some cases and that has contributed to an increase of rents and prices in double digits in some cases. i.e Mafra 10% rent increases last year and Setubal +15% price increase.

That 4% mortgage is a real asset.

When you build enough capital/assets/net worth to afford a reasonable monthly cushion you can see if the lifestyle of a full time investor is something you’d want to pursue.