Im not sure I fully understand the mechanics of it but with your experience, it'd be great to hear your perspective. 

The addendum specifies they cannot do mechanical work in the garage (e.g. oil changes), they are for storage only and I am not responsible for the contents.

I am a mechanical engineer, and have been working in the industry for almost 7 years.

Subtract the hours you expect to sub for mechanical/electrical work.  

My feeling is that you don't have to worry about various licensing authorities since it does not sound like you were working as a realtor.What you may want to consider is taking the path of a mechanic's lien.

No technology can protect you from that.Whether you work with a bookkeeper, a contractor or an auto mechanic - you have a lot at stake, and relationship controls everything.

In addition to this I am also a certified Red and Blue Seal Heavy duty mechanic I can most definitely help with automotive questions relating to anything with an engine and associated electronics.

If we also replaced mechanicals, roofing, siding, windows then that number is 2%. 

@Mikel Kaubfa it’s more about the mechanics of metering than it is a decision to include or not include.You have to have each utility separately metered in order to charge a tenant.

This doesn't mean it's too much, just prepare for something more expensive that putting new mechanical in an existing home.