If you aren't familiar with it, Bolt Action is a Skirmish/platoon level wargame set in WWII, designed for 28mm figures. The game was written by Alessio Cavatore and Rick Priestley, and published by Warlord Games and Osprey Publishing. As you might have guessed based on the authors and scale, this is 40k for WWII. Thankfully there are some great rules innovations. Instead of players taking turns moving and firing all of their units, players draw dice from a bag to see which player gets to activate a unit next. There's a mechanic for suppressing fire. Close combat is rare, but decisive. It seems to be a great set of rules that makes for a tactically interesting game.
From a modelling standpoint, there are plenty of great miniatures out there. While 28mm is the suggested scale, as that is what Warlord Games is selling, it would be very easy and economical to use 1/72 scale figures and tanks. The armies aren't that large generally, so the cost should be prohibitive. A typical army consists of 30-50 infantry plus leaders, an artillery piece, and armored car or recon vehicle, a tank, and possibly some transport vehicles. Standard 1000 point armies are available for $120. If you want to jump in feet first, they have a whole Pegasus Bridge set for $280.
For an old 40K fan that loves history, is working on a budget, and demands a solid ruleset, Bolt Action is not to be missed. I'm hoping to get some games in at Cold Wars next month.