If you're going to Jess Yen's shop you'd be foolish to get a backpiece from anyone but Jess Yen.
Foo dogs are a great subject for a backpiece, especially with peonies. You should probably listen to your artist when it comes to placement.
But if you can't afford a good backpiece, don't get one. Now is not the time to go bargain hunting.
My advice: Get the best tattoo you can. Money is secondary. If you can't wrap your mind around that one, you're not ready to make that kind of commitment. The reason many tattooers can't quote you a price up front is because it's hard to know how long a piece of that size and scope will take, but I'd guesstimate you're looking at least 25-50 hours – 100 on the outside. Hourly rates are mostly meaningless because some of the best artists are very fast and some newbies are very slow. By trying to get a bargain you could end up with a mediocre to bad tattoo that's way more expensive than the one you could have had.
Take the time and save up while you make up your mind. And/or consider getting one foo dog on an arm or a leg and take it from there. From everything I've read, however, you're probably not ready. Feel free to prove me wrong but don't ignore good advice from people who know more than you.