When you say "not a mecahic," do you mean not a vehicle mechanic, or not at all handy? There's a difference; being handy with typical household repairs and maintenance--things like caulking or adjusting cabinet hinges or minor appliance repairs--is very useful for keeping an RV in shape, even if one is somewhat clueless about the details of transmissions and engines and whatnot. Even better is being willing to tackle something you didn't previously understand based on YouTube videos, forum posts, etc.
Anyhow, for a class C motorhome (and probably a class A as well), the actual chassis bits are perhaps the simplest to keep working; it's basically a slightly overgrown van chassis, and for the most part they're pretty straightforward to work on and pretty reliable, though of course there are various parts that wear out with use and time. Basic work like topping up tires, changing oil, etc. is about the same as on any car, and sometimes easier because there's more room to access many parts and more space underneath the vehicle to worm one's way around.
Keeping the rest of the RV in shape is a more or less constant series of little things, such as resealing/recaulking holes and seams, keeping propane appliances clean, replacing the odd compartment door holdback that snaps off, finding and tightening a loose wire, and any number of other odds and ends.
In terms of economy, a used motorhome often offers the best value as the initial depreciation is significant and presumably on a used motorhome any build problems from the factory have been fixed. When buying used, how thorough the previous owner(s) were with their maintenance and upkeep is quite important to consider, possibly more so than age or mileage or brand. Of course, finding a layout that works for your family and systems that meet your needs (things like tank sizes) is also very important.
I would suggest giving some thought to how whatever unit you're looking at would work as your children grow. Many RV bunks, for example, are pretty short, and might be fine for an eight year old but in four years when they're a lanky twelve year old and a foot or two taller would be quite inadequate.
Almost certainly the most cost-effective RV for six people, though not the most convenient or luxurious, would be a pop-up camper.
