Hall or Meeting Place to Use

You might check with your local church to see if they would make a room available for free or for low cost. They probably would if this was presented as a public service, more so then as a profit making service. So you might teach an introductory class free and then let those that are interested, sign up for follow up classes.
I do like your idea of a networking seminar for moms with home-based businesses. I know several crafty moms who combine efforts and hold two craft fairs a year to sell their crafts. You could also do an on-line newsletter to promote each others businesses.

Check with your church or your local library.
LBC

Chek out your local Panera bread. They usually have a conference room. I beleive it is free of cost or minimal.

You may want to check with your local library as well. Most have a few community rooms that can be used (along with town halls, etc). But, you may have restrictions if they're based upon business promotion. They'll be able to let you know the restrictions in place.

Also check your local parks and recreation departments (through your city or county) as they frequently have indoor meeting spaces. Locally, ours are free if you're within the municipality and minimal cost if you're outside of it.