I was going to propose to the seller carrying a note w/ a second pos. on deed for 30% of purchase price.

From the IRS, regarding what is tax deductible: “There shall be allowed as a deduction, all the ordinary and necessary expenses paid or incurred during the taxable year in carrying on any trade or business”.

This method carries significant risks to both parties.)A loan assumption, on the other hand, is completely legitimate, and can be a great way to acquire a property if the existing mortgage rate/term are competitive. 

@Stan Chigintsev, re CAPEX: I try to carry a $5000 reserve on every door to account for the major issues: roof, HVAC, major appliance, etc.

One of the credit cards I carry recently offered me a cash advance special where I could access up to 95% of my credit limit ($35,000) at 0% interest for 13 months.

I picked up the 2x4 and carried it like a bat, ready to swing. 

In my inexperienced opinion, if you can cover carrying costs and are confident in the rent/value appreciation, a deal that looks bad at first glance can make sense long term.

Do you require tenants to carry rental insurance even if you have the property insured?

I'm carrying a lot of losses from previous renovations.

They have to take responsibility for their belongings or carry the risk.If you do decide to require it, you will not be able to enforce it.