23109VC here is a link to a book about prety easy built in projects. I am posting it since you mentioned wanting to build closet organizers.

Really easy and inexpensive closet organizers. They are pretty basic but very functional. The section that the cover photo is from covers how to make them from MDF.These are paint grade. I have built them in a couple of houses including the one I live in now. You can buy baskets and bins and build the shelves and cubby holes around the sizes you find or get the baskets and bins that fit later. If you like the project I can give you some pointers that would make it even easier. Just for example an example of the cost, a twelve foot wide wall closet would be about $250 for materials including paint.