To get a picture of it, just consider the idea of having four bedrooms' worth of guests every night, preparing a hot, delicious breakfast for them every morning, and cleaning up their rooms every day.
Then add onto that the need to help your guests find their way around town, market your inn, keep accurate records, do household maintenance and yard work in a timely manner (can't let that grass grow too high!), and do everything else necessary to run a bed and breakfast. And at a small bed and breakfast, you'll be doing it all yourself, or with your significant other -- hiring help only becomes financially realistic in mid-size and larger inns.
Yes, being an innkeeper is a very demanding job. It has plenty of upside, too, but don't lose sight of the very real work that's involved.

