So far I have not had good customer service. 

Therefore right now I'm considering using a service for submetering and then billing separately (currently I live in the ADU and rent out the main house).Does anyone have experience with this? 

Basically, you ask permission from the mortgage servicer, who then informs the mortgage investor assuming they are good with it.

We don't allow any "deal-making" in the forums, which includes advertising your services or properties, looking for partners, etc.

I hope you are asking two separate unrelated questions, because there's no point in doing cost segregation for properties held inside your self-directed solo 401k, save for some very rare exceptions.Some of the Bigger Pockets experts who operate reputable costs segregation companies are @Bernard Reisz, @Yonah Weiss and @Julio GonzalezSome of the Bigger Pockets experts who offer Solo 401k administrator services are @Dmitriy Fomichenko, again @Bernard Reisz and @Brian EastmanReach out to them and see if they can help.

Personally, I enjoy self-managing and screening is my favorite thing, so I'm not in the market for PM services, but a lot of my clients that I work with and other fellow investors would be interested in it.

I should note that that I was using Baselane's banking service to collect deposit and rent, and had moved the funds immediately to my private bank after I collected (thank god!).

Securities and Investment Advisory Services offered through DFPG Investments, LLC.[1] Multnomah County Executive Rule No. 388, March 11, 2020[2]Marcus & Millichap, 2020 Multifamily North American Investment Forecast

In this market there are cabins on their own land and cabins on leased forest service land.

It should be as easy as converting one conventional loan that cashflows well to a Debt Service Coverage Ratio loan or DSCR.