There's this idea of a T-shaped skill set that I think very much applies to this kind of business: You have your primary skill (i.e. the service you offer, in your case engineering expertise), in which you have in-depth knowledge, and then you have supporting skills (like accounting) in which you're no expert but which you know sufficiently well enough to be able to market your services.
Finding the right balance between earning sufficient revenue sustainably (and the always reasonably full sales funnel required for that) and not taking up more work than you can handle can be particularly stressing.
Solid advice, I might add the wisdom Alan Weiss is a must read for new consultants > https://www.amazon.com/Million-Dollar-Consulting-Professiona...
The biggest stressor for the owner's of most small businesses is not getting a regular paycheck.
Good luck.
Go for it!
1. What tactics do you use to ensure a stable income? 2. What percentage of your time is spent actually developing?