Their wage is not what they cost
The number you agree is the start of it. On top sit payroll taxes, workers' compensation, liability coverage, their share of a van, fuel, tools, a phone, training, and the time you spend managing instead of working.
That total, expressed per productive hour, is their labor burden, and it is the number that goes into your pricing. The gap between the wage and the burdened cost is routinely large enough to wipe out the margin on a job if you price off the wage.
There is a labor burden calculator on this site for exactly this. Run it before you agree a wage, not after.
They will not be billable for a while
Even an experienced tech does not know your customers, your prices, your paperwork or your patch. For the first weeks they are slower than you, and you are slower too because you are answering questions.
Budget for that honestly. The common mistake is assuming week one produces a full week of billable work, discovering it does not, and panicking at the end of month one about a decision that was always going to look like this at the start.
Everything in your head has to come out of it
A one-person business runs on things the one person knows: what that customer was told last year, where the stopcock is at the house on the corner, what you charge for that job, which supplier has the part.
None of that is available to somebody else. This is the real reason owners say hiring did not work — not that the person was bad, but that the business was never written down, so every job needed an interruption.
Before they start: get your prices onto a price list, your customers and their history into one place, and the way you want a job done written somewhere they can read it.
Decide what they can see
A new tech needs their jobs, the customer's address and history, and a way to log hours and photos. They do not need the margin on the job, the full customer list, or the billing screen.
Setting that up on day one is much easier than retrofitting it after an awkward conversation about why a tech was looking at what the company charges versus what it costs.
Employee or subcontractor is not a preference
Classification is determined by the nature of the relationship, not by what either side would rather call it, and getting it wrong is expensive — back taxes, penalties, and potentially an insurance claim that does not pay out.
The rules are federal and state and they have been changing. Before you decide, speak to an accountant or employment advisor in your state. This is the single most expensive thing to get wrong on this page and it is not something to work out from a web page.
Watch the first month closely, then stop watching
For the first few weeks, look at every job they finish: the hours against the quote, the photos, what the customer said. You are calibrating, not supervising.
Then deliberately stop. The point of hiring was to get work done without you in it. Owners who never move from the first mode end up with two people doing one person's work and an owner who is more tired than before.
Expect the second one to be easier
Almost everything hard about the first hire is one-off: writing down prices, setting up a second van, learning to hand work over, finding out what people actually cost.
The second hire inherits all of it. Shops that stall at one employee have usually not finished the first-hire work, rather than hitting a real ceiling.