Very good points thus far. Here's my .02 as a charter guy:
If you can break into the charter world at 1500 hours I'd say you've done quite well. Most of those jobs companies want guys with 2000-2500 tt with about 500 multi time.
Insurance companies dictate the times required more often than not. And if you've mostly done straight flight instruction, that would not be as appealing to a company as prior experience as a freight guy, or regional pilot. I would advise one of those jobs as a stepping stone to get where you want to go. Would it cost more or less to insure a CFI than say a regional FO/freight dog? That's what you'll have to deal with.
Paying for your own type is generally not looked upon very highly. It takes a fair amount of time to get comfortable in a jet. Yes a type can possibly open some doors for you, but not as many as you might think.
Personally I notice a difference in my flying when I've not flown for awhile and then hop back into the Lear, even if it's only a week. Most of the captains I have flown with say the same about themselves. I went through a period of about 6 months when I had been out of the Lear, and it took awhile for me to get back to being where I felt I was truly competant, even though I had about 500 hours in the jet. If you don't use the skills you lose em. My point is getting the type and not using it right away, and often, will not help you very much.
Also, time in type is critical as Jason said, but actively flying that equipment is very important too. Say you pay for the type and can't get much work until it's recurrency time for you, will you be able to foot the bill to go to recurrent and then continue waiting for the work to appear?
So my advice would be if you really want to be a freelance biz jet pilot, fly charter for quite awhile first, and to make it to charter flying you may need to be a regional pilot/freight dog before that, and all that while: network network network.
Further edit: Thanks for the link Jason, very informative!