This seem like a very last minute decision to get into breeding, IMO.
That being said, how many times do you plan to breed her? Will you be neutering the boy? A cycle, "heat", will last around 2-3 weeks. and happens about every 6-8 months.
2-3 litters was all we did for our girls when we bred pits (this was about 10 years ago) and we ALWAYS waited for her second heat before breeding.
What kind of contracts do you want for the puppies. Do you want spay/neuter contracts, do you want to require finishing for the dogs.
Are you breeding the two you are adopting together? How will you handle the separation of the parents while she's pregnant, or after she has the babies?
One issue i came across was that the male in our house didnt like the puppies, and tried to get at them, any time he could. My family also bred dachsunds, and the mom was HORRIBLY aggressive to anyone who tried to get near her puppies.
I cant talk about the costs of vent for pregnancy, because it was so long ago, but we didnt go that often. They arent pregnant very long
At this point, i would really suggest contacting the breeder you are buying from and asking them a lot of questions.
This website seems to have some good info, but appears to be about 5+ years old.
Does have some good follow through reading on the birthing process.
http://www.marvistavet.com/html/body_care_of_the_pregnant_dog.html
This one seems pretty decent as well.
http://www.dog-spoiling-made-easy.com/care-of-pregnant-dog.html