. - The commercial property is in an LLC, we get K-1s from the LLCs taxes every year showing that the LLC pays for the expense and is cashflow positive; except for the deprecation we take :) I plan on buying a new primary residence in the next 1-2 years and want to know if I need to have the commercial loan adjusted so that its no longer personally guaranteed.

But, I would personally be very uncomfortable using a HELOC as a traditional down payment option. 

I will add that investing in a real estate syndication where you have Unrelated Business Income Tax (UBIT), if you are going to use a self-directed IRA, you might be better off using a Roth IRA, instead of Traditional IRA, due to the tax-free compounding growth of Roth.

One big takeaway is that MTRs function more like short-term rentals (STRs) than traditional long-term rentals.

This approach can help you secure funding more easily without the need for traditional income documentation.

I’ve been learning about the industry / different regional markets for the past few years and am eager to execute my first deal in the near term and continue growing through this community.My primary goal is to purchase a property I can live in while generating rental income (e.g., a single-family home with a tiny house, a duplex, or a single-family property where I can install a tiny house).

For your first question about doing a "subject to" on a hard money loan, it’s possible, but it’s not as common since hard money lenders typically have stricter terms and might not allow a loan to be assumed like a traditional mortgage. 

I look at it through the lens of: 1) If I contribute to a pre-tax account like a pre-tax 401k, Traditional IRA, SEP IRA, I get a tax deduction, but now I'm in a partnership with the IRS, but I don't know what I will have to pay them later on in life when I start pulling money out (that is because when you distribute you pay taxes based on your effective tax rate at that time, which can be unknown). 2) With Roth accounts, (Roth IRA/Solo 401k(k) with Roth component), I can get the taxes out of the way on the seed, so I don't have to pay on the crop. 

I'm familiar with the big 3:1. Sell home: ideally avoiding capital gains tax by living there for 2 of the last 5 years2. Cash-out refinance: this is a little painful with current interest rates3. HELOC: good for short...

Does not work as ideal brrrr even if numbers play out for traditional ideal BRRRR as there is no way to extract all cash invested.