While there are powers that grant temp hp and others that negate hits, I still don't think it's terribly feasible to make a character with a minion in tow for any serious encounter. The damages are just too high to be easily countered by temp hps. Average monster damage at that level is about 18, so you'd need a lot of temp hps to counter that, and there would be a razor-thin margin for error. After all, if they lose all the temps you give them, they are one away from dying.
One way I can see to make this remotely work would be to use a houserule to allow the temp hit points given by the artificer's Healing Infusion: Resistive Formula to benefit from a feat like Lend Health, then apply both of those ideas to the base leader class you are looking at running. Similarly, a Cincture of Vivacity and a Shield of Fellowship would give you a way to transfer a lot of temporary hit points to your minion. Those are level 14 and 15 items, though.
Potions of Vigor (level 9 -- 15 temp hit points for one of your paragon minions's two surges) combined with some way to give the minion Resist to damage would be useful in prolonging his life on his own "fuel."
Immediate Interrupt powers that mitigate damage (like the artificer's Shocking Feedback) or buff defenses (like the Warlord's Powerful Warning) could be used to extend the viability of your minion. Maybe a kind DM would let you scour the classes and take the best of these for a given level and modify them to suit your primary attribute.
As to the money aspect, I have a hard time justifying spending that sort of cash on what is basically a consumable. What sort of potion would your level 10 character buy for 3000gp? (Granted, this is a "potion" that has the potential to last a week or so, but then again, it might get "lost" in the first round of the first fight due to a lucky crit or high damage roll.)
You might be able to do some serious re-fluffing with some sort of animal companion class/build/theme (beastmaster ranger, fey beast tamer theme, sentinel druid, etc.) to get sort of a similar idea, but with more durability. If I were wearing my DM hat, I could see a fey beast tamer refluffing a displacer beast companion into a rogue buddy or an owlbear into someone like Mongo from
Blazing Saddles (big, dumb, "barbarian"/brute), or similar. The Thrallherd paragon path for psions is similar. (In fact, I think the thrall they get is only slightly different than the fey beast tamer's pet.)
Well, I hope that helps.
