It's not always "all or none". See if you can go "half-way" to employment: ask for a 6- or 12-month contract for a fixed fee per month for 40 hrs of work per week. If you work more than that, it's up to you. You know how much each check will be.

You get to see how a full-time gig works for this boss, and you get as much "job security" as you probably would as an employee, anyway.

What you give up are the benefits (insurance, 401k, etc.), if there are any for a small firm, but often the flexibility is worth it.

I had this relationship, renegotiated yearly based on their (and my) needs, with the same company for 14 years. They have since reorganized and I now do projects for them on an hourly basis.

Get creative.