What is a good assumption to use as a percentage of gross rents for Repairs & Maintenance and also Capital Expenditures?

I'm looking at a deal and the seller is saying you can pay all cash, get a new loan or assume existing loan with 5% interest until Sept 2018 then jumps to 8% after that. there might be a 1% assumption fee.

I am making an assumption that $2400/month in Georgia is a Class A property.   

Negatives; hes in breach of contract as my lease states no subletting, I have no idea if he has the proper insurance, he's outright lying to me, hes making more money on MY investment than I am (assumption).

One thing I wish I'd known at the beginning: spreadsheets, and calculations, and all that are based on assumptions.

Also, and we aren't wired to file many insurance claims but my assumption is that actual home insurance doesn't cover typical items that require maintenance over time? 

Also, the property is in an okay neighborhood.Values with squigglies are estimated.Asking Price:  $94,500Closing Costs:  ~$2,500Rehab:  ~$500Down Payment:  20% ($18,900)Prepaid taxes, insurance, and interest:  ~$1,000 (not sure how to estimate this so this is just a guess)Initial Investment:  $22,900Mortgage Remainder:  $75,600Mortgage Interest Rate:  ~4.5%Mortgage Period:  30 yearsMonthly Payment:  $383.05Monthly CostsProperty Taxes:  $167Insurance:  $50Utilities:  $0Lawn Care/Snow Removal:  ~$50CapEx:  $100Vacancy (5%):  $61.50Repairs (5%):  $61.50Management (10%):  $123Total:  $996.05Total Monthly Rent:  $1,230Cash on Cash ROI:  12.3%Do my assumptions seem reasonable?

It will depend on the current condition of the property and quality of tenants.The Future Assumption Information makes this more confusing.  

Any information or assumptions would be appreciated.Thank you.

There’s also this assumption that interest rates will be the same, access to capital will be just as easy, etc.