Personally, I don't like the idea of random people potentially having keys, but I'm OCD about security and key control (most people aren't).One potential option going forward is kwikset smartkey, which can be easily be rekeyed yourself between tenants. 

More control on how much you actually pay per month and you aren't paying if you aren't using it.

I would plan to pay for majority of upgrades with a line of credit.I have a few additional reasons beyond monthly cash savings to sub-meter the electric: 1) There is one thermostat in the house, controlled only by tenants in the largest unit.

I got a 12 unit last year and I really believe my cash offer gave me control of the deal.

I buy properties by "taking over" the mortgage & the payment of the mortgage and then I control the property.

I’m currently licensed in termite and pest control.

I like to have control in most situations to ensure the right people are hired and the right solutions are implemented but I can see a benefit to asking the seller to deal with it. 

The MOMENT you change a rule for a tenant, you have lost control. 

By doing this, you'll be able to ask more specific questions and get more precise advise on what to do when it comes to a flip.

There are things that they would be entitled to in terms of a price adjustment (in your example, if lumber prices skyrocketed for a specific reason beyond his control then usually the owner is on the hook, however, there are measures to limit this exposure).A contract can be drafted using the scope of work, estimate, and schedule (you can include liquidated damages - this is a sum (not a penalty) of what it would cost you if the project is not completed on time - think daily rent and storage rates).