I learned this lesson as far back as the late 80s.
Ive still got a 5k sqft shop, with 4 bays, 2 lifts, and includes everything you will find in a well equipped Indy shop and then some, even OEM service info for the big three, as well as all data. Ive also got a fab shop, and even own toys like a Huth exhaust tubing bender. Turns out, I like buying shop equipment and tools.
In the event anyone asks for anything, I typically just don't reply.
Now, I have a Dr., who has moved mountains to improve my health successfully, and I will do just about anything she asks ( she is single and has allot to take care of, I act as a jack of all trades for her ), and take no money, and my farm hand, I will fix his car for free, I even put tires on his car, and other random parts at my expense, because he is really good help.
Otherwise, the rest of the world can kiss my ***. I got out of the repair business for reason. I love fixing stuff, but I hate dealing with the *** hats that own the vehicle, which is why I flip stuff instead of repairing for hire. Everyone has money to buy a vehicle or toy, nobody has any $ when it comes time to repair it...
And family, I learned the hard way, is the most entitled, wants the most, and is the least likely to pay, even for their own parts. Even after they formally solicit your advice on what to buy, and then goes and buys the one POS you told them not to, and then they want you to keep it running, ugh.
There is a long list of people I only hear from when they " need " something, and its always a want, never a need. As I like to say " your lack of planning does not constituent a crisis on my behalf "