I’m not a traditional earner, I’m a self-employed musician, and in order for me to get a conventional mortgage, I’d have to pay about 40% in taxes each year.

One company owns everything and does nothing (this is your SLLC a/k/a “asset holding company”) and a completely separate company handles all of your operations (this is a traditional LLC a/k/a “operating company”) For the operating company which serves as your face to the world and through which you do all your business, you establish a Traditional LLC to carry out the operations of your investments.

Today the SEC came out with this as part of their complaint against a defendant selling private securities:"Respondents did not have pre-existing, substantive relationships with a number of the Fund’s investors and engaged in a general solicitation of public interest in the offering through Fund's website and traditional media interviews."

It is nice to have some funds in after-tax Roth funds and some in traditional Pre-Tax accounts so you can control how much tax you pay.

Question: Is it possible/permissible to open a SEP IRA and make contributions from my real estate LLC while simultaneously maxing out my traditional employer-based 401(k)?

10% down is unlikely with any kind of traditional financing?

You are right traditional lenders don't like renovation loans and expect much more documentation than a hard money lender for that type of loan.

My thoughts would be to combine the traditional business of storage or mixed use storage and business or traditional storage with creating a delivery service similar to Clutter (less advanced of course). 

Be sure that you highlight that "selling your house can be easier than you think" with the advantages of working directly with you instead of the more traditional route

Traditional loan How did you add value to the deal?