Very well put Bonfire. I am another vet of the industry (15 years) but had to finally get out 2 years ago. Just know going in, if you are not a lower level employee, the restaurant runs your life...at least it did mine. I have worked every position in the restaurant from dishwasher to bartender while going through culinary school, kitchen manager, store manager and ended in corporate. It may have been the situation I was in, but I couldn't take the hours and not seeing my family anymore. Like Bonfire said, if you like cooking as a hobby, get ready for that to end.
What is your situation? Will you be a silent investor? Accountant? Store manager? Owner?
If you are owner, will you have someone manage the store for you? Can you trust them? You shouldn't.
-There is so much theft in restaurants: topping off someone's wine, bringing out a side of fries for a buddy, employees walking with product. Little things like not charging for extra sauce or not charging for a soda really start to add up. Will you be checking in on these little things, or are you entrusting someone else for this? If there is someone else, will you be following up to ensure their pars and counts correct?
-Restaurant can be a revolving door of employees, many of which do not have the same vested interest as you. Yes, you can get someone that works their butt off because of work ethic, but unfortunately, these people are few and far between in this industry.
-Again, like Bonfire said, everything costs something. Margins are already so razor thin in restaurants so little things like breaking a plate, not ringing up for soda, line cook hitting overtime add up fast.
-Where is this place going? Take Houston for example...is it going to be a hip place near Montrose or will it be family friendly out in the Katy suburbs? What is your clientele? Lunch spot or dinner? Kid friendly or no?
There is a reason so many restaurants die and people always say "don't do it!" If this is your dream, go for it. Just know there is so much more than just cooking food. If this is a hobby...well...good luck. It took me 15 years for the dream to finally die, and I couldn't be more happy now. There are probably a hundred other little bullet points I could add in on what to look out for, but that would take a while. Just know that not everybody has the same story. Some have succeeded and many have failed, but cannot get out of the business because of their love for the industry.
Good luck with whatever you decide to do, and hopefully you can figure out if it is right for you or not before you get too far in.