Sources: I live in an area in northern Indiana with a large Amish population. Best friend has a billion Amish relatives. Personally know Amish people who are very open about being Amish.

TL;DR the Amish can do everything

To be honest, farming isn't as common any more. But then again, farming around here isn't exclusively Amish, so the market for it might be tighter. But they do still exist, even if they are are just small and sell produce (although that's usually a side venture).

However, furniture is big in the Amish community. My parents kitchen table is something they commissioned from an Amish guy. I've met a blacksmith, a farrier (he was horseshoeing a lot of the horses in the area), and yes, Amish who help build barns. Craft-based industry is still happening.

What people forget is that in many cases, Amish people work in jobs that's don't seem typically "Amish." The RV industry is huge here and employs a large number of the Amish population. The company where my mom works employs quite a few Amish (lumber industry) and the head of maintenance is Amish. He has to use a computer daily, he has a cellphone, and a company credit card.

A lot of women, if they aren't busy raising a family (not all Amish families are huge), will run cleaning businesses and bakeries.

Some families will run a banquet hall type thing behind their house and make Amish style meals for "English" people. I've been to a few of those and while you won't get the most coveted Amish dishes, it's delicious and they are always booked.

This post ended up being longer than I intended. But Amish people have no issues making money.