Rick posted quite a few of the questions I would ask, but being someone who very recently purchased an existing and fairly stable sign business, my experience is very fresh. Thankfully, I have 34 years of hands on sign experience to compensate for the things I overlooked, ignored and was prevented from seeing.
Get practical, pragmatic advice from your CPA AFTER he or she has studied the companies books for the last 3-5 years. If it doesn't pencil out, you aren't going to undue a systemically weak business model, no matter how good you are.
Is the company covering its overhead expenses? Bottom line, is there enough profitable work to keep the doors open, the lights on consistently and everybody, including yourself paid a living wage?
If not, you are not going to suddenly turn it around given your lack of hands on experience.
What condition is the major equipment in? How often has it been serviced, cleaned, etc. How old is everything?
Unless you want to pay part of your profit out to IT services, computer repair and troubleshooting services, etc. regularly you better get some real hands on experience on how to fix the day to day glitches and problems that arise with these printers, laminators, etc. that we use all day.
How is the lease on the shop? You have to have somewhere to work and expecting his loyal customers to find you in a new, unfamiliar location is a stretch. Humans are nasty creatures of habit.
Can you get access to his sales records? If so, pull up a bunch of average jobs and see what he was charging on average.
Is it below the local going rate?
Was he the lowballer in the community or somewhere in the middle?
My predecessor whined a lot to me about how low ball everyone else around here is, but in reality he was the one driving the market down. I've struggled to justify to loyal customers why their jobs cost more and to gain the trust of my colleagues that I'm NOT like my predecessor.
Lastly, collections and accounts receivables. Was the guy, Mr. Nice Guy and couldn't collect on an invoice? This is our single biggest struggle. We knock the work out of the park and our track record for service is awesome, but even the most regular customers will not pay on an invoice until pressed multiple times. We've since implemented a solid deposit system and our cash flow is good, but we always carry a lot of dead weight around very month.
Good luck and frankly, get more hands on experience. Every dollar you pay others to do tasks you should be doing yourself is future dollars you won't make and won't reap when you sell to the next person.