No, they have to pay their own health insurance in Germany and deal with taxes themselves as a self-employed person. Additionally, most likely they have to foot in for pension and a couple of insurances to be on the safe side. Germany is €€€.
I’d also recommend getting a Steuerberater. They’ll need it. Mistakes are expensive. And don’t spend any money in the first year. Second year taxation will be 3x the nominal rate: tax for the first year, most likely full prepayment for the second year and quarterly payments of 25% for the following year. Ah, and Gewerbesteuer, unless they qualify as Freiberufler…
As a german freelancer for >8years, I can confirm and highly recommend you stick to exactly this advice.
You will also have to check with the tax authority (Finanzamt) whether you can become a "Freiberufler" (all income taxed as personal income) or whether you need to register a business ("Gewerbetreibender"). Whether or not the Finanzamt accepts your status as a Freiberufler depends on different jurisdictions, there is no uniform decision making in place. Most will grant you the status if you have a university degree in Engineering (or Computer Science). If they decline it, I would recommend to create a limited liability company (GmbH, stay away from UG). In any case, get a tax accountant to assist with this.
> yes but at least his taxes are paying for healthcare and other social services
This is not exactly true in the german system. Social insurances are separate from taxes. For example I am a self-employed German, and I am exempted of paying into the government pension fund (as a result I am also not eligible for pension and have to make my own arrangements). Same for health insurance; while you cannot be legally exempted from it, you can be exempted from the government system ("gesetzliche Krankenversicherung") and pick a private health insurance company (which has its own advantages but also drawbacks).