If you’re not knowledgeable about these things you could have a home inspection done and ask them to point out any obvious signs of upcoming large capital expenditures (new roof, furnace etc.).  

Often times the landlord in student housing.Long-term capital expenditures (roof, siding, etc.)Bad debt / unpaid rent (though your 10% vacancy factor will likely more than cover this if you are in a decent market)Legal (hopefully little to no costs)Advertising (A lot of free options these days so you may not need any budget here)Personally I think the maintenance factor is about right (Usually between $50-$150 per unit, per month - higher for single family / older properties).

Your CAPEX reserve (set aside out of NOI), is budgeting for when you will need to make major capital expenditures in the future (roof, windows & doors, HVAC, appliances, etc).  

If so, that is leaving out property taxes, insurance, maintenance fees, capital expenditures, and property management fees, so that $250 dries up pretty quick. 

Depending on age and condition the property is in you can assume $250-500 per unit annually for maintenance and $200 per unit for Capital Expenditures.

Now I too am a DIYer, however, my suggestion is to utilize either loan to take care of the big capital expenditures to have that out of the way for the next 15-30 years such as the roof, HVAC, upgrading electrical panels to separate utilities, etc. 

A lot of small multi families give you all the docs you need rent rolls, bills, summary pages, repairs/cap ex expenditures.

The CapEx should be reserved for just that - capital expenditures, things such as new AC, roof, water heater, etc. and the maintenance line should be used for monthly maintenance like fixing a leaky sink or general repairs.

Certain capital expenditures can be expensed and certain need to be depreciated.

We ended up buying the cheapest house in a upcoming neighborhood, so after capital expenditures I still have a strong cash flow.