My gorgeous mutt was a rescue, from Many Tears.
She was found, with her siblings, zipped up in a sports bag that was left in a car park
. They estimated she was about 6 weeks when dumped, she was about 10 weeks when we got her. Later on my vet said she thought Mutt was more likely 2 weeks younger. There were 6 of them, and I think one didn't survive 
We applied to rescue her by completing the online form. We had a 5 yr old DD at the time. The form asks an awful lot of questions, we answered them all truthfully and in detail, including the fact that Mutt would also spend a lot of time with a 2 year old boy, and a very young baby.
About a week after we applied a homechecker came out, bringing her dog with her. She had a good look around the house and garden, asked lots of questions (things like as we were in rented did we have the authority of the landlord, and the proof. How would we deal with housetraining, where would dog sleep etc).
She also watched keenly as DD played with her dog, and asked DD a few questions.
A couple of days after the visit we were told we were accepted and could collect Mutt from a foster home, we all had to travel to get her and we had to take any other pets with us. We were warned that if the foster mum wasn't happy we'd have to go home empty handed.
Foster mum had 2 of the pups, it was a mad house! DD was beside herself and wanted us to have both. Happily we came home will Mutt and she has grown into a wonderful amazing dog, DD's best friend.
We didn't know for sure what breed she was. MTAR suggested Springer/Collie, but we think there may be some whippy and pointer in her. She's a Mutt basically!
I wouldn't get too hung up on what breed to have. If it is a pup you are getting then you can mould it into whatever you want. The only thing I would say is that you should be honest with yourself - Mutt has 3 walks a day - and needs at least 2. No matter what the weather, no matter how busy you are, you have to be committed. If you can see yourself looking out the window and thinking "I don't want to go out", then a pup is not for you. Similiarly we used to wake up some Saturdays and say "lets go into London" or "Lets go to the Safari Park". We can't do that any more - activities have to be planned. Mutt can be left (shes 2 yrs old now) but I think it is unfair for more than a few hours. Luckily we have a friend who is always happy to have her. Oh and holidays - if you are going to use kennels (I wont) then plan that cost too.
If you want a pet with less committment to walking etc then an older dog who may only need a quick nip around the block would be better.
(Ex racing Greyhounds are fab for this so I've heard
)
Hope that helps