Looking for preferably a tele stock, but more importantly the cheapest that is readily ava. (shopping used)  Will pretty much all AR related (Colt/BM/DPMS/RRA/Etc) all interchange?

Mil-Spec tele stock parts such as Colt, LMT, Stag Arms, CMT and Vltor won't interchange with commercial size parts of Bushmaster, DPMS, RRA, etc.

Commercial type buffer tubes have a larger diameter than the Mil-Spec type tubes of the noted brands.

If commercial type buffer tubes are larger in diameter to Mil-Spec tubes how does anyone attach the commercial type buffer tubes to a mil-spec lower receiver?

Quoted: If commercial type buffer tubes are larger in diameter to Mil-Spec tubes how does anyone attach the commercial type buffer tubes to a mil-spec lower receiver?

Only the outside diameter of the buffer tubes are larger at the rear of the threads, threads size and inner diameter are the same.

Both commercial and Mil type buffer tubes will fit any lower receiver.

If you have a commercial buffer tube and install a Mil-Spec type stock, the stock will not fit and could get stuck on the tube.

When a commercial type stock is installed on a Mil type tube the fit will be loose and have more play.