Is there a percentage to respect ? 

The better the terms the higher that percentage could become. 

Good idea for the percentage row, I am going with LTR, thank you

If you think about it, the more equity you have in the deal, the lower their risk yet they still make the same percentage return on the capital they lend out.

Get one really bad loan, you wipe out a significant percentage of your capital.  

With your experience in Nursing I also thing it is a great idea to learn about MTR since you have connections within the nursing industry which makes up a large percentage of the MTR target consumer.Other than that, speak to those who have accomplished what you are trying to do.

What should be the value of raw land (in percentage) from a given price of a built house ($750K)?

I'd venture to say that the percentage of valuble info, after you've ingested most of the content out there, is no higher with paid content then with the free content you will curate for yourself.  

What's better, sfr just you or the small multi fam with a significant percentage of the mortgage paid by tenants?

I would be willing to bet a very small percentage of people on BP majored in specific degrees.