Help running numbers on Seller Financed Buy & Hold

[Devan W.]

Hello BP! My aunt is wanting me to buy her SFR because she no longer wants to "deal with tenants". She doesn't want any interest from me and basically just wants me to take over her loan. She currently has the basement rented for $500/month and upstairs is vacant. Market rent is around $700 for upstairs, so total income potential of $1,200. Utilities are currently included with rent.

Listed below are all the numbers. I think it's a solid deal but the seller financing part is throwing me for a loop. Just not sure how to factor it into my numbers. Any help or advice would be greatly appreciated!

3bd/2bath SFR
Purchase Price - $70,000 (pretty close to market value)
Her current loan balance - $50,500 @ 4.5%. She has 22.5 years remaining on the loan.
Down Payment - Initially will be $14,000 (will use my HELOC at 6.25% interest). Then she wants an additional $6,000 paid out over the next 2 years to equal $20,000 total. This basically gets her principal back & the money she has into the house.

Est. Repair Cost - $2,500
Property Taxes - $1,450/year
Insurance - $843/year
Loan Details - Payment is $531/month. This includes taxes, insurance, P&I. Loan has 22.5 years remaining. Can I just leave the loan in her name and take over the payments?
Electricity - $55/month
Water - $60/month
Vacancy/Repairs/CapEx/Mgmt - $96/month for each. Figuring 8%. I will self-manage but still wanted to run the numbers at 8%.

Can someone please walk me through the numbers, specifically Cash on Cash ROI? Looks like I would cash-flow a couple hundred bucks a month and could be more if I make the tenants pay for utilities.

The COC ROI is really confusing me after trying to factor in my HELOC interest and initial down payment PLUS additional $6k over 2 years.

Any other details that I need to be aware of? Would I still have tax advantages if I left the loan in her name?

Thanks BP!!