Hello!

Myself and 4 friends are planning to do a three week long loop from SF down the coast to San Diego, then head towards Vegas/grand canyon and then back to SF via Yosemite, stopping for whatever/wherever we fancy.
We're planning to do this as cheaply as possible, at the moment we are thinking of renting a minivan and buying a big tent from walmart or somewhere, then staying in motels/airbnbs for the bigger cities and camping in other places.

Firstly, does this seem like a decent route to people that know the US?
and is the time frame quite reasonable for us to take it at a fairly relaxed pace while seeing all there is to be seen on route?
Is there anything else off route really worth visiting in your opinion?
we think this works out a lot cheaper than hiring an RV the whole way, because of Rv hook-ups, extra fuel cost, and absurb RV rental costs. does this seem like a cheaper option?

We would really appreciate your opinions on the route, things to visit, as well as anything cost related that I've mentioned.
Thank you!