I am looking at starting my own maintenance shop somewhere other than Iowa. I found an opportunity in Washington state that I am looking at. I have all most of the numbers I think I need tallied up and the shop looks to be profitable. I would start a 145 as soon as I could (have the basic books done already). Does anyone here own their own shop? Any big things I should be looking for buying a business? Hidden expenses I am not thinking of. I currently run a shop so I have most of the basics down but thought I would pick arfcoms collective brain.

My dream. Unfortunately no longer an option for me (physical). Have you looked into Rotax 912, 914, 915 Level 2 or greater?
I have a friend with an LSA that is running into issues finding warranty repairs. You also want to have capabilities or at least easy access to avionics service, especially Garmin.
Unfortunately, my Part 145 experience (2xDOM/Chief Inspector) is pretty out dated and I've found FSDO cooperation varies greatly by region, but regardless you need to make friends with the inspectors. I got along with the senior guys a lot better, not trying to score violations and more willing to go out on a limb when making judgement calls.
Where in IA are you planning to set up? I grew up in NW IA, SW MN a long time ago. How big of operation? Flight school/rental? Sounds exciting!
I'm pondering the sale of my tools and equipment , but my youngest daughter (14) is considering becoming an A&P.

Well I am hoping to get out of IA. The market here is oversaturated with people pencil whipping 1950's Cessnas lol. With the 145 avionics would be on the docket. I haven't looked into rotax training. I should probably I just haven't had the opportunity to work on a rotax in 5 years! I would probably start small just two guys but would want to move to avionics and maybe flight training.

I understand. And then there's the freelance IA's working the T hangars out of the back of their pickups. Another option I was looking into before my injury was providing builder assistance to home builders. You provide some assistance with building basics up to and including complete build completion. And the liability is nearly nonexistent, they are  experimental. I performed annual conformity inspections on several home built airplanes. All of them were professionally built.

I love some homebuilts.  I have a small biplane myself that's a homebuilt (didn't build it but still put a lot of work into it. )  It is hard to make a living as a small shop so I want to specialize. I have always wanted to restore planes so that with avionics in the right location I would think a guy could do ok.

145 means you will have plenty of opportunity to get to know the local feds.  As already mentioned, there is regional variation in how likely you are to end up viewing that as a good thing.  Worth doing some research on, when looking for a location.

Restoration is a bit of a niche market, and there is a tendency for shops to become specialized within that niche, due to the skill sets needed for some projects.  Each project will eat up a lot of time, taking up shop space even when you are not working on it (doing other jobs to keep the cash flowing, etc).  Not the easiest business to keep from going broke in.

I've worked for two companies where refurb/mod work was supposed to be their primary business.  Seemed to be cycles of juggling to squeeze normal maintenance work into the schedule, to keep the finances out of the red.