I have to say you have been given some very good advice here - as a breeder, based on what you've said thus far, you wouldn't get past first base with me.
There are people with dogs who work full time, but they put a huge amount of thought and time into how they manage having a dog - it is not a commodity to be thrown away if it doesn't fit - it's a long term commitment of 10 years + - with some of the smaller breed possibly even up to 16 years +.
If you really are serious, then a golden oldie from a rescue is a better idea, but I would still have my reservations - sorry