Buying a pregnant goat - what to look for?

So this will be your first goat...and heavy bred at that? Wow. That can be both exciting and scary. Are moms first time moms or experienced? I would not want to bring home a first timer being this is also your first. Look for many of the same things as you would an unbred doe..healthy shiny coats, clear alert eyes, famacha is bright red, pooping berries, active(although being heavy bred may make her a tad lazy...it sure did me lol)
Check out her udder and teats...look for good attachment on all four sides and Good size teats. Teats should point somewhat downward not outward or too close together for easy milking.
Ask how they did last kidding and if there is anything you should look out for. Definitely ask to see the buck.
Do know the stress of moving them so close can cause early labor. Give probiotics and b complex to help with stress when you get home. Make sure any dogs or other critters won't rush her or challenge her..give her her own space to settle in along with lots of attention. Might bring an empty gallon jug and fill up with water at her current place..so she has something that taste like home...then add your water as needed. Just a little extra step to help her acclimate since she is so heavy bred. Ask for a few days of her current grain and make her food change slowly if not feeding the same. And if you can managemore than one goat..two buddies make any move easier.
And if you never helped a goat kid before...lots of reading 😉

Beat wishes

Pretty much everything happybleats said. Does the herd you're buying from test for CAE, CL, and Johne's?

Gosh, I wouldn't even sell a doe who is that close to her due date. The stress of moving to a new farm and the change in routine so close to her due date would be so stressful! And the birthing process can be such a trial by fire (my first kidding experience was horrible!) I wouldn't want that for a first-time goat owner either. Is there any way you can leave them at the farm until the kids are on the ground?

I actually lost a sale last year for that very reason, the buyer wanted to pick the doe up 2 weeks before she was due. I told her no, that it would be too stressful and that she could take the doe once the kids were a few days old. She bailed because she wanted her kids to be able to witness the birth (???) Well, that doe had a difficult delivery, wouldn't have been able to get the kids out without help, and 2 of the 4 kids died. There's no way my buyer, a first time goat owner, would have been able to handle the mispositioned kids and would probably have lost the doe too.

If you do decide to go for it, besides the advice happybleats gave you, make sure you have a vet's number on hand ahead of time who you KNOW will be able to come out in the event of an emergency. If you have an experienced goat mentor or neighbor, have their number on hand too! Give the does lots of quiet, keep them hydrated, give them probiotics, and it wouldn't hurt to give them a dose of Replamin too.
Good luck!