First when we don't know much about investment, we just want to buy door, one door,two doors etc etc...but then we progress, and we make business alignment with other third party, we could become flipping.While owning door is not passive, it's 70% active investment, flipping is 200% active investment.It involves and requires a lot and a lot business planning, business connection, market strategy and such.......while renting is something like any kid with 2 million dollar can just throw a dart in Cleveland and would buy multifamily in that city.

If a lender goes to their supervisors and says it is ok, I would put it in writing so that you are cover in the event that the stars align and someone checks up on you. 

The rents/activities passing through the LLC to S-corp would be the rental income on the S-corp books,  that would not align with your goal of separating two businesses. 

For the typical kind of rehabs that I aim for I consider 20% a good ROI if it is aligned with the time, risk, hassle involved.

I have an agent I know I can list a property with and something might happen if the stars align (he has a very big name behind him).I also have an agent that I know I can call and a property WILL be sold.

So, his interests are aligned with mine -- maximum profits, quick turn-around on projects, etc.Basically, the goal of having a project manager is to allow me the flexibility to focus on building the business (finding deals, creating processes, defining strategies, raising money, etc), without having to worry about the day-to-day aspects of the projects getting done.

Another way we've managed our HELOC is to deposit all of our income back into it every month and aligning all our bills to be paid at the beginning of the month.

But see #1 & #2 above if you've borrowed money against it as this is not a blanket statement.5) Align yourself with other folks and be ready to capitalize if things go bad. 

It is also important to have a solid understanding of the local real estate market and to continuously look for new investment opportunities.Ultimately, it is essential to have a solid investment strategy and to work with experienced professionals such as a realtor and a financial advisor to ensure that you are making informed decisions that align with your long-term goals.

Then once you've answered them, pick a strategy that aligns with your goals (fix and flip, buy and hold, wholesale, etc).