Any way to befriend other charecter on same server/account?

[HEC-]

I suppose if I want to get money for other char I can make him sell something for 100k and buy it as main char.

In such case remember that you'll pay 5% listing tax so you'll end uk with only 95k on other character unless you'll menage to do it during decreased tax period (then it will be only minus 3%) and indeed you need to purchase it in the same state where it was listed otherwise you'll pay another 5% tax. The best way to transfer between characters on thesame account is to have your own FC - cost you only 15k to establish and need one friend to help you with that for about 5 minutes.