Well, I’m a firm believer that so long as you’re not trying to up-sell yourself into something your not and you stay within your social circle and they know you’re just starting out / been at it for a short while and are willing to pay you.. I honestly don’t see any problems with it.. So long as you’re honest about it.
As far as starting a business goes? I’d suggest you hold off.. Not because you’re terrible or anything but when people that don’t know you start paying you, you have to be able to change gears in a hurry and adapt quickly.. I don’t know as I can’t see your EXIF data, but I’m assuming you’re probably using a 3.5-5.6 kit lens with that 3100 and a popup flash.. So, waiting wouldn’t hurt so you can save up and invest in some faster lenses (better gear) and more experience.. Even family can be hardcore when they pay you..
Additionally, a business involves:
Registering a name with the State
Getting a Tax ID
A physical location (preferably not your living room)
a legit business anyway.. Good luck 😀
I am sure others will add to this 100 fold.