​How much money should I have before I hire an employee?

I am currently running a one man plumbing company. My reputation is good, but I typically have more work than I can handle without working insanely long field hours.

After I finish up these jobs I will have roughly $20,0000 in cash. I have credit up to $8,000 that I use to purchase material for jobs and so far it’s been enough.

I want to hire someone who I can send on their own without my supervision and for this I’m going to need to pay at least $30 an hour. I charge $100 an hour.

I can expect to hit dry spells where I don’t have much work especially in the winter and ideally I would send the employee to jobs during this time so he or she can continue to be paid when work is slow.

Is $20,000 enough to commit to bringing in a full time employee without risking not having the money to pay him? I estimate that on my own I am doing what will be $150,000 – $175,000 in revenue a year. Roughly 50-60% of that is profit with me being the sole employee and I expect it to be 20-30% with the work the employee would do but I haven’t done the math to see if that’s right.