that's easy  mortgages double in some case .. and they were sub prime borrowers and a huge amount were minority don't understand what they signed... and walked. ergo there is NO sub prime any more.. and this is why home ownership is so low in areas that are heavy to minorities ... and those areas have turned into rental areas with landlords from out of state.

When buying an older home from say 1920-1940 are there certain things that should be double/triple checked before moving forward? 

I thought I could only purchase single fam homes with VA, but I will double check and see if we can do Multi fam, I lean more towards that goal. 

If you have an 8% CoC investment, and you figure that you are putting 30% down, and that you will get a 4% increase in sell price per year (and assume you can increase Cash flow 2% a year (you should be able to do better, but keep it conservative) .. break out a spreadsheet and do this your self... you double you cash in 7 years, you will see 40% come cash flow and 60% come from increased market value... so you have to sell to see your profits.Most investors, can not handle getting so much value from the increase in RE prices.. that is why it is a tough market... also that is why I got out.

The loan counts as home-acquisition debt for which qualified residence interest deductions are allowed, as long as the applicable home acquisition debt limit ($750,000/$375,000 or $1 million/$500,000) is not exceeded.Bigger standard deductions: For 2018-2025, the TCJA almost doubled the standard deduction amounts.

Like double sink vanity or double shower head?

Even if we could double the houses being built, we still wouldn't have enough housing for the expected inflow of people.

It's on a better street and double lot but the house is in worse shape than the one in the video.

They did not hit double digit returns.

I have lent to flippers before and would expect double the 9% yeild if I was taking the risk on an individual properties.