Input from experienced users... if this is a daily driver, stop right now while you are ahead. It is never fun to wrench on something you have to have back together to drive immediately.
Get an economical vehicle, start putting money away. If you have a large trust fund and you want to deplete it, send us a list of your wants and we can put together a plan to spend it all.
In a few years, you will realize the value in paying yourself and saving.
You can nickel and dime away $20G without even realizing it, trying to polish a turd and keep up with the Joneses. That same $20G would earn you interest, or become a down payment on a house, or even buy an almost new car.
There is almost no end to what you can do to a vehicle, but at some point, you have to ask yourself, is this worth it. Changing an engine, transmission or other powertrain component isn't rocket surgery if you can access some tools and a hoist.
Body work and paint can be expensive. If the paint is overly thick or crazed, you will need to strip to bare to repaint, figure 40 hours in a shop to chemically strip the exterior and get it back in primer ( ext cab 8 foot bed ) ready to spray. If the body requires extensive repair and panel replacement, that adds to that figure.
If it is truly going to be a toy, then you might as well start with the newest, most rust free sheet metal and components that you can afford.
00-05 would be where I would be looking, 5.3L equipped 1/2 ton 4x4. You could pay more and get a 3/4 ton 4x4 with the 6.0, but you have to ask yourself is the juice worth the squeeze. Going with large tires and planning on a lift, then perhaps a 3/4 ton would be a better fit.
The sky is literally the limit.