It is all about the price and who gets to cash who out. If the owner sets a ridiculous price you’ll have to put a lot of sweat equity in, and then you’ll need to double it or even more to buy him out!
Arrange to meet with the owner’s accountant so they can give you a financial overview of the business. You should also look at getting some free Small Business Agency help via their SCORE program https://www.sba.gov/local-assistance/resource-partners/score-business-mentoring You may also want to look at going to a community college for business classes or if you already have a degree going for your MBA if you really want to grow this business big time.
Reach out and see if they are willing to send out a message to their customers referring you for future service. Often times you can buy the customer database inexpensively.