I work from home one day a week (Paid from my employer), but I didn't start doing this until DS was about 15 months old. The first few months were very difficult, it wasn't until DS was closer to 2 that it became much easier. Prior to that I'd only get a few hours done during the day and catch up all the rest at night. I definitely couldn't have done it when DS was under 1 as he only every slept for 45 mins at a time.
I guess the best advice is to have realistic expectations and set yourself lots of mini goals, and realise that some days its just not gonna work at all