if the electrical needs to be updated, that is OK as long as that is factored into the numbers, and as long as you have someone competent to do it.  

You would want to check local zoning to make sure you could build more than one as a lot goes into that beyond just being close to plumbing, electric, and gas.When you mention "a lot goes into that beyond just being close to plumbing, electric, and gas," what are the top things people tend to overlook when preparing to build ADUs?

But larger repair items such as appliances and mechanical, plumbing, electrical, roof windows doors etc should still fall under the landlord's responsibility.

Have a salon with a water heater that was installed around three months ago, and the tenant has complained that it's having issues heating the water; I suspect it may be an electrical issue with the system. 

Take this opportunity to upgrade your plumbing and electrical if needed. 

Optimally, the lawyer or the firm should be familiar with public infrastructure that developers are typically asked to pay for, such as road widening, turning lanes, new roads, sanitary sewer extensions, new water and electric extensions, fire hydrants, etc.

It is difficult to recapture the electrical savings from the tenants. 

Cost to run city water/sewer and electric service (it's already at the street)3.

Break down your rehab into individual jobs, for example get a electrician for electrical work, a plumber to repipe the house, a dry wall guy to close out the walls, etc.

If all your plumbing and electrical are in place that would reduce it some but not down to $20,000.