I got this idea in my mind, when i saw popular mods opening Patreons to continue development. Well yes, these are big projects and is required a lot of time for their final realese, but i was thinking... what about a freelance job? like, someone ask you to program a weapon, an entity or a NPC in their mod for a few bucks (of course, for a very very cheap price).
Tho most of the projects i've saw where made by a lot of people with no financial motivations, i see a few cases where someone was willing to pay money just to code a few things (at least on Moddb), so my question is: How probable is to find people who is interested in your coding habilities and wants you to do a commission in the Source engine? or even more... in the Goldsrc engine? They are very old engines and i don't think there's that much demand for coding of these like in Unreal or Unity. (Also because most of the people who moddify very old games do it for their own projects istead of economic reasons, just like i do, i don't really want to tie my projects with monetization)