Advice on E1 Visa?

I am interested in the E1 Trader visa, but the stipulations of the Visa seem vague. My parents and I have had the following 3 businesses. Could any of these be reworked to qualify for an E1 trader visa?

1. Kindle book publishing business
I hire ghostwriters to write fiction books for US readers. At the moment the ghostwriters are based outside US, but I am hoping to hire US ghostwriters. As part of the business, I research US culture. For example, a recent title was set in Arizona, so I had to provide my writers with photos and details of Arizona that I had acquired from a visit there.

2. Accountancy business
My parents have been running an accountancy business for the last 30 years. At the moment it only deals with UK clients, but would acquiring US clients satisfy the E1 trader visa?

3. Property portfolio
My parents had a portfolio of properties in the UK, which they have mostly liquified to build a similar portfolio in the USA. Would their American tenants satisfy the E1 trader visa? If not, then would buying US furniture satisfy it?

Other business
If none of these satisfy the E1 trader visa, then what business can I set up? I used to be a web/graphic designer before going into publishing. Would a digital agency with US clients be a good business? If not, would exporting/importing a certain type of product be better. If I do go the exporting route, then can I sell online or do I need a physical store?

Also, how long does the business have to be running and how much revenue does it need to qualify?

Please note, I am not looking for a quick fix solution and appreciate that making a suitable business that qualifies for E1 Visa takes time.