We have a 40' DP as well. Wow. So many things, if you're a newbie. Guess I'll be devil's advocate here.
Coaches don't do well sitting for long periods. They need to be run. And not just up and down the highway for a half hour then put back in storage. Speaking of which, have you checked on storage costs where you are? You could pay well over $1k/yr just to store it. Plus the licensing and registration. And insurance. Figure all your costs, as best you can, annualize it, then divide that by the number of days per year you realistically expect to use it. That'll be your cost per day, plus gas.
When are you getting out? If you put that $57k in a good investment, earning 10%/yr, how much would you have when you got out?
You didn't say how often you'd use it. "Weekends and holidays" doesn't, to me, sound like justification for an expensive, relatively high maintenance, complex coach.
I was in the Navy too, and I know it's easy to get anxious about something like this. Based on the little info you put in your post, I think I would wait, and save like a madman until you get out, and then buy.
Why?
1. Coaches depreciate terribly. I bought a coach which sold, new, for $230k. I bought it when it was four (just 4!) years old, for $93k. Can you believe that? And in beautiful condition. If you were to put that $57k aside, and add to it as much as you can, if you could have, say, $90k when you got out, imagine what you could get! Something that's brand new today, might be in your price range in 5 years!
2. Coach quality and innovation are improving. You're looking at a 12-year-old coach. A LOT has changed since then; even more will change, and get better, over the next few years. And this one is just getting older and older. You WILL have things go wrong with it, and repairs ain't cheap. Mine is an '05, being maintained regularly, and things still go wrong. I'm taking it in tomorrow for $700 of *preventative* maintenance.
3. Does your coach have slides? I googled and saw one of your model with two. That's nice....but....as a full-timer with 4 slides, I can't imagine life without all four. And with a family of 5? And when you get ready to sell the coach, or trade it in, fewer than four slides will really hurt its value.
I just think, if it were me, I'd wait and get something really spectacular when I could use it a lot, or even full-time. It ain't the price of the dog; it's the "pup-keep".
If you do decide to go ahead, you might consider a PPI (Pre-Purchase Inspection). Lots of RV dealers do it; try to find an Tiffin-authorized shop. Probably cost $400. But it can really be worth it. When I sold my first motorhome, a guy came out with a buyer's checklist he'd ripped from a magazine. I saw him checking things off a list as he walked around the coach. If he'd had a PPI done, he'd have discovered that the side of the coach, while still completely usable, was beginning to delaminate (outer wall separating from the inner wall). Caveat emptor! (Let the buyer beware).
Thanks for your service....
dave