Intangible assets like goodwill or tangible personal property (e.g., equipment) are excluded from 1031 treatment and are taxed separately—goodwill is typically taxed as a capital gain, while equipment may be subject to depreciation recapture taxed as ordinary income.To minimize taxes on the sale of the business, consider strategies such as Opportunity Zone investments, which defer gains until 2026 if proceeds are reinvested in a Qualified Opportunity Fund (QOF), or structuring the sale as an installment agreement to spread taxable income over multiple years.

However, i would like a person with multiple rentals to help guide me to avoid some simple mistakes.

The key is that in order to completely defer all tax you must purchase at least as much as your net sale. 

even if its interest only, id want to pay down principal here and there. seems like sellers would offer this interest only route so they have 0 capital gains tax, but id rather pay down a bit of principal in 7yrs. i see its not required but it should allow for principal paydown in promissary note3) any general advice to look out for on seller financing?

Otherwise, probably not as they know they can get out of a significant debt by running from and avoiding it and have shown they will do that. 

Working with Real Estate ProfessionalsLocal Real Estate Agent: Choose an agent experienced in student housing.Property Management Services: Consider hiring a property manager if you’re not local.Inspection and Appraisal: Conduct thorough due diligence to avoid costly repairs.6.

You can hear real-world examples of how others have built their investment portfolio and (hopefully) learn to avoid their mistakes.4.

Any advice on what setup is easiest and most tax advantaged?

What's even more frustrating than asking the IRS help desk, is asking a Turbo Tax "Tax Specialist".

Yes, do the tax exchange if you can.