"Come to Mars!"

"Build a Better Tomorrow!"

"Start Over in a New Life![1]

"Free Transit, Food, Clothes and Shelter![2]"

"Only a 5 year contract!"

[1] new identities and Martian Citizenships issued after a simple medical checkup

[2] air and water are not included in this great deal

There are people already willing to go on a one-way ticket. I don't think it's too hard to believe.

They are provisionally willing, I'll put more weight on that declaration once they are on their way.

I also speculate that there are a number of people willing to go for historic prestige (or something like that), while most potential indentured tickets would have to see some pretty terrific economic prospects at the other end of the contract (it's warm on Earth and the air is free).