Ahh I see, that makes it a little different. Where I am, there are actual visas for this case (called a fiance visa). I'm not sure exactly what they'd be looking for to prove a bonafide relationship (possibly some evidence of correspondence), and it does require that you've met in person at least once within the last two years. Not sure where you and your partner are based, so again, YMMV.

Once married, I expect you or your partner would apply for permanent residence (a "green card"). This is where you'd have to show combined finances, etc. If you have the means, consider consulting an immigration lawyer in whichever country you intend to reside.