You and your Solo 401(k) are distinct taxpayers in the eyes of the IRS,Trump tax reform has precluded the "netting" of income/loss from separate business activities that are subject to UBIT.If your objective relates to #3 (above), there would be benefit derived from a cost seg study - assuming the Mobile Home Park investment is truly subject to UBIT.    

I'm also unsure if deducting mileage on personal return for business travel expenses was eliminated by the tax reform?

Thanks, Adrian Yes, that book is updated yearly, and it's important to get the latest edition, due to the recent tax reform that changed the game substantially.Even better - hire a tax professional experienced in real estate.

So the tax reform just got its first approval, but I’ve been trying to read up and understand how this will affect my rental property real estate taxes. 

Prohibits an RGB from setting longevity rentincreases.Part D: Repeals High Rent Deregulation, which allows units to be removedfrom rent regulation upon vacancy after the rent achieves a high rentthreshold; and Repeals High Income Deregulation provisions, which allowsunits to be removed from rent regulation if a tenant's income is$200,000 or more for two consecutive years.Part E: Sets the Preferential Rent as the base rent for the duration ofa tenancy, but preserves regulatory agreements that allow for legal rentincreases.Part F: Allows HCR or a court of competent jurisdiction to look back at6 years of rent history when determining rent overcharges, or a longerlook back period if it is reasonably necessary to make a determination.Eliminates the ability of an owner to escape punitive damages where theovercharges were willful.Part G: Enacts the "Statewide Tenant Protection Act of 2019" to allowany city, town or village to opt-in to ETPA and provides the appointmentof the members of the new RGBs to be done by the opting-in munici-palities.Part H: Amends the maximum collectable rent increase formula thatapplies to Rent Control units to set annual increase at either an aver-age of the last five years of RGB increases, or 7.5%, whichever is less;and prohibits Fuel Pass-Along charges for rent-controlled tenants.Part I: Reforms the personal use exclusion to limit the number of unitsan owner can take out of rent regulation, and requires the use to be animmediate and compelling necessity for use as a primary residence.Part J: Ensures that units rented by nonprofits to provide housing tohomeless or previously homeless people revert to rent regulation at theend of the use by the nonprofit, and that the previously homeless personor persons are treated as tenants for purposes of the law.Part K: Major Capital Improvement (MCI) & Individual Apartment Improve-ment (IAI) Reforms*Limits approvals to work for essential building functions and otherimprovements (e.g, heat, plumbing, windows, roofing); exclude mainte-nance.

Please add other relatedhttps://www.jacobinmag.com/2019/06/new-york-housing-tenants-universal-rent-controlhttps://ny.curbed.com/2019/6/14/18679507/rent-regulation-new-york-state-reform-legislation-passedI'm in Rochester, NY and looking to invest locally where I can oversee my properties with a reasonable drive.Does this primarily impact only unethical landlords?

They changed after the recent tax reform, specifically there's no longer $100k home equity option. 

https://www.nysar.com/docs/default-source/legal/2019-nysar-landlord-tenant-reform---memorandum.pdf?

@erikbaumer Here are two other good summaries of the 2019 law changes: http://www.realestateindepth.com/news/things-to-know-expansion-of-rent-regulation-and-tenant-protection/https://www.nysar.com/docs/default-source/legal/2019-nysar-landlord-tenant-reform---memorandum.pdf?

Make sure they’re also aware that tax reform restricted 1031s to ONLY real estate.