Is this a common method or not?

Here are a couple of methods of pipe replacement that I am aware of you might be interested in looking at.https://www.youtube.com/watch?

@Lolo Druff Real Estate Investing is not like Trading Stocks or Crytocurrency.Real Estate Investing requires some deep thought and research from you as an Investor.Having 400k to deploy to multiple duplexes is a great start but you have some questions to ask and answer yourself.

We are a team of five employees, and our work involves renting land for a number of years, designing and developing buildings, and managing them—including renting and maintenance.It’s an exciting yet challenging new chapter in my professional journey, and I’m eager to learn and grow alongside all of you.One of my key goals is to modernize our company’s workflow, which is currently reliant on traditional pen-and-paper methods. 

Income from a trade or business where a taxpayer doesn’t materially participate.2.

Since all these Companies are publicly traded, you can read their yearly 10K'S and quarterly 10q reports. which are very transparent as to how they generate their profits and what risks their seeing on the horizon.

If LL uses accrual method, they can book revenue without receiving.  

If I did the BRRRR method would this work out perfect?

You can also use the Enemy Method to check the rates of your competitors.

I have investors that I set up loans with private money that only use this method because of the speed.