I am figuring that my rehab budget takes care of anything I know about at the time of purchase, but I am also putting money aside so that when my furnace goes out or it's time for a new roof, I have the cash available. 

On larger properties, outside of performance calls, owner's usually get involved if there is a big bust in the budget (to alter the business plan if needed), capital expenditures are going to be more than estimated (find ways to cut costs if possible), or leasing strategies need to be adjusted to keep up with other competitive properties (example: providing concessions on new leases or renewals). 

When her contractor quit, I had to jump in and take care of it personally and worked on the property few days.

Yes, they have a responsibility to pay rent, to take care of the place and it is important that we hold them to that but I (we) have a responsibility to provide and maintain a place based on the expectations of the lease and how we market it. 

Not that you have to go see it yourself, but you should hold people accountable to ensure your property (investment) is actually being cared for.

@Catherine Stevenson I have previously dealt with unresponsive property management and contractors and have found that it is better off going your separate ways as soon as possible no matter what the loss, it is often better to cut ties right away. 

But I was exploring the possibility of her getting some down payment cash and 3-5 years of potential cash flow instead of taking whatever that non competitive market gives her after the agents take their cut.

To the contrary, I think its a great idea but you need to be very, very careful. 

Take care and good luck.

Be careful with pro-forma estimates, 45% operating budget on a fourplex isn't unreasonable at all.One thing I may suggest is starting to run deals like this by a commercial lender- residential lenders don't even look at the property's ability to cash flow if the buyer is strong.