They will get sick but most employers will understand. The sickness lasts about 6 mo's so save up vacation time or perhaps you can work from home.
I have used home daycare and regular with my two, 6 and 2 yr old. I'd go with home daycare at first. They do get less sick and it's an easier transition for them.
The good news is that my kids are rarely sick now. It was just the initial daycare sickness.
Now if your child is always sick it could be a sign of something else. I thought it was just starting daycare. My son had sinus infections for 6 straight months. The ENT wanted to do sinus surgery but my husband said no way and we got another opinion. It's turns out he's just allergic to everything. He takes allergy meds and is no longer sick.