She quickly ordered an inspection and sited 3 very small items which have been rectified.

I don't disagree that it is a huge budget item.

One guideline I use says that if the rent is $1000/mo, then the most I can pay for that rental (including any renovation) is $80,000.One caveat though - if you purchased that $80K property and it had plenty of deferred maintenance (needs a roof, windows don't work properly, old HVAC, galvanized plumbing), then you would need to have these items fixed prior to purchase or factor in this maintenance (pay me now or pay me later...).  

The first few months, she had to sort through what was for what, and we went through a few items, but now she knows, and she just logs into my accounts at various places and can get all the info she needs.Trust me, unless you LOVE numbers, get a bookkeeper.

We have a plan in place to put some money (5-7% of the purchase price) into it (mainly cosmetic items) to be able to drive higher rents in about a year.  

Only moving 2 walls, moving kitchen from one end of a room to the other, and rebuilding a deck, but other than those two items it is all just finishings.

When handled properly, it should keep your business acquisitions away from your personal items.  

If results of said inspection reveal (A) additional large items of repair or maintenance needed without prior knowledge by buyer or (b) additional repairs where estimates add up to 1% of the sale price; the buyer may renegotiate the terms or rescind offer." 

If you want to spend a few extra minutes you can save even more on items doing the following:For Lowe's I've gotten up to 34% off: Sign up for Post office mail forwarding for 10% off coupon, shop discount gift card sites for above 10% off gift cards (the best I've gotten was 18% off), buy the gift cards through topcashback website (1-4% off), purchase gift cards with citi double cash credit card for an extra 2% off.I bought a Neato vacuum that retails for $500 for $364 (shipped to the house) using the same method above except substituting the 10% off mail coupon from the post office with bed bath and beyonds typical 20% off. 

You were missing a couple key items Property Management, Management, Repair Rate etc.