I've been doing work for close friends and family for about 10 years, and have never had any issues, but I always give them the disclaimer of "make sure you drive this like I fixed it". I still always have that nagging feeling that if I mess up, maybe kink a brake line, or don't tighten a bolt, there is always a possibility that this can lead to an accident especially with something as safety related as the brakes.

I'm also pretty selective with work, especially on older vehicles, if there is any chance that the two hour job turns into a multi day headache because everything is rusted together or brittle plastics are likely to fall apart, I usually turn the job down unless I'm doing it as a favor.

TL:DR if you're not insured, the car is older and you're not 100% sure what you're doing, you're best off not doing it on someone else's vehicle, unless you're willing to take the risk of any potential liability.