Allie,

First make sure the 3yrs financial statements include the federal tax returns...unless the statements are audited and signed by a CPA, you should consider them next to worthless.

I don't think you should get your expectations too high about increasing the business significantly with a website. I've never looked on the internet for a detailer to do my car and I question how many people do. That money might be better spent on good signage and local advertising.

It doesn't make a lot of sense to spend time and money on a media that exposes you to hundreds of millions of people, when only those in your immediate area are actually potential customers.

As far as the asking price for the detail business. Because it's an individual that currently owns, runs, and does the work there's a higher risk of losing customers with a ownership change than if the customers had a relationship with a number of different people where most were going to be staying. I certainly wouldn't pay more than 1x the net profit as supported by tax returns. This means that if you manage to maintain most of the existing customer base it'll pay for itself in a year.

Your training plans etc are too convuluted for me to comment on so I'll just assume it's something you feel will work for you.
Good luck