Tia is pretty well off for a mercenary, but for the time being she has no intention of contributing to the group funds.
To be honest, I'm surprised anyone is willing to put money into the little tugboat since it's about to fall apart really. XD Vellios is understandable as he's a risk taker and honestly, as long as he can survive it's not a big deal for him. He can make money fairly easily because he's pretty much open minded and rather... good at getting a job done when he's got a mind to.