I have seen non compete clauses in employment contracts and termination stating 6 months or 1 year. If you do not have that as part of your previous employment then by all means compete as best you can. As a side note I am not a fan of one man shops I prefer at least 3 engineers so that you can eventually get to a point where you are training eit's.

Nothing unethical at all as long as you don't, as GeoEnvGuy pointed out, have a non-compete in a contract with anyone.

I've been going through a somewhat similar transition. I was working for a firm but got an offer in a connected but different industry. I was able to leave on excellent terms and, as soon as restrictions lift and it's safe to do so, we're all still planning to go get a beer together. Well several months after I left, I started getting some calls from people asking if I wanted to do some work on the side. I decided to go all in with it and get the appropriate licenses, insurance, etc. It's still a part time deal (my current employer doesn't offer services to the public, so I'm not competing with my employer or violating any no moonlighting policies), but it's technically in direct competition with my old employer.

I went ahead and contacted the leadership of my old firm and let them know that I was doing it. I'm making a point to not market directly to their clients, but that's a matter of personal choice rather than ethics - and I'm also not turning them away if they call. Before you make the plunge, you may want to reach back out to those old clients and remind them of the conversations you had and see if they still feel the same way. Maybe they've settled in with your replacement and don't want to change. Or maybe they found another firm and they don't want to go through another switch so quickly. Or maybe they're sitting around every evening drowning their sorrow over you moving away. (We'll hope for some version of the last one!)

I have the luxury of folding up shop and just working my regular job if I so choose, so I can afford to maintain that bridge better than you may be able to. I'm also not in a position to really compete with them on the big money makers, anyway. That's an important thing to consider. What size projects are you taking on? There comes a point where it's just not feasible to do the design, calculations, drafting, etc. within the time frame of many projects if you're by yourself. So for now I'm one of the detestable "bottom feeders" that picks up the minor inspections, repairs, the odd addition, etc. One day I'll grow out of it, but for now I'm not capable of operating at the same level and won't try because I'll end up doing a disservice to the client and the engineering community. That may be something to think about. After all, ours is an industry of relationships. A firm's true value is in the relationships it is able to make and maintain, which means the value is in the people. If they can't keep the people who hold the value, then that's their fault (usually). You have value and you owe it to yourself to use that value for the benefit of you and your family. If your old firm can't respect that, then are they really the sort of people you want to maintain close ties with?

Non-competes are not enforceable in certain states, although even then certain restrictions on information usage might still be a de facto non-compete provision
https://www.legalnature.com/guides/are-non-compete...

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

This is the business version of going out with your best friends ex gf a few months after they parted.

Never ever works out as you would like. ...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Thanks for the feedback! There was no non-compete contract. I started working there shortly after graduating when I was an EIT, so I don’t think my boss had thought much about it. So I know I’m fine there. Reaching back out to those clients is a good idea! I went ahead and called one and he said that he’d still follow me anywhere I went and that ever since I left my old company had been drowning and his projects as well as some of my other clients projects have just been sitting there because they haven’t replaced me yet. So I know I’d at least have him as a client and it sounds like some of my other clients would be very interested as well if my old boss can’t keep up the work load. I would certainly stick with smaller projects to start with so I wouldn’t really be taking a huge chunk of my old bosses income. I hope he’d understand, but I guess if he doesn’t I need to just not worry about it.

Business ethics are tricky sometimes. I am like you and do not want to do anyone wrong. However, there is not much you can do to tip-toe around this one. My recommendation would be to mention to your old boss in an email or text message that you are stepping out on your own. I would not mention clientele. If he brings the topic up, just say something to the extent of, "I have a few interested in my services", and leave it as purposely vague as possible. As you well understand, providing for you and your family should always come first. There is no harm in that, and what you are doing is not illegal or unethical in the slightest in my humble opinion.

So long as whatever communications you have with your previous clients do not have the appearance of "poaching" them, you SHOULD be fine. Just bear in mind that there's not much of a bar for filing a lawsuit, so it's best to keep things ultraclean.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm