Most people don’t see the difference between a 300$ and a 3000$ camera. Sometimes they even think the cheaper one is the more expensive one because it looks bulkier.
And even if they know that, just be honest, offer them some pictures as a thank you and you will be fine. We all started somewhere. Good luck and have fun!
Besides the information already posted here about noise and grain, I might have to add something to the way you seem to perceive ISO.
Increasing ISO while keeping the same light-conditions would rather decrease(!) your noise. There is a lot of misconceptions regarding ISO. The ISO (in digital photography) is simply working as a gain for your light, resulting in higher signal and noise levels. BUT, the noise you see is not dependend on how high your noise level is. It depends on how much more signal than noise you have. And as long as you don’t blow out your highlights, your signal to noise ratio stays the same. But if you shoot underexposed you decrease your signal to noise ratio and that’s why we think raising ISO adds noise. Because in that case we start using higher ISO and realize that we start seeing the noise. But compared to postproduction the camera still works with far more signal than in the resulting raw-file, meaning that increasing the ISO will introduce less noise than increasing the exposure of the Raw-file and shooting with high ISO results in less noise than increasing it in Post-Production.
Don’t believe me? Try capturing the same scene normally exposed with high ISO and than underexposed with low ISO and raise them to the same level of exposure in postproduction.
Yes, same thing with studio lights etc. Truth is, most pictures don’t require bulky cameras, big lenses and fancy studio lights. But people take you more seriously when you have them. That’s why some wedding photographers I know have a cheap DSLR with a big lens around their neck but only shoot with their smaller mirrorless. Simply because they can charge way more that way. And I mean, it’s stupid, but it works. So it ain’t stupid.