What type of visa for the USA?

Hi,

I'm a stock photographer & am planning an extended trip of 5-6 months to the US. Visa Waiver only allows 3 months, so I'll need to apply for a visa.

For that, I need to go for an interview at a US Embassy – who often want to see a prove of income (i.e. royalty statements / bank accounts... to demonstrate that I can finance myself for the period of my travels).

Most of my income is from stock photography – and of course, I'll be doing stock in the US. But I'll also spend a lot of 'leisure time' there...

So, does this mean that I need to apply for a business visa? Or can I apply for a standard tourist visa?