The UK doesn't have a visa for trial relationships or for open-ended cohab with friends. The question comes up all the time, and people are invariably disappointed to learn about the expense and the rigmarole.
Depending upon the relationship you have with your friend, you will need either a fiance visa (6 months) or a spouse visa (a probationary term of 30 months). Both of those require that your friend earn at least 18.6k in salary along with accommodation and so on.
If it isn't a romantic thing, then you would need a Tier 2 visa to work for your friend's father. That requires that you have a really great skill and will earn a minimum of 35k salary. It also requires your friend's father to have a sponsor license and those are hard to get. Since you're asking on the net about it, I assume your friend's father hasn't been briefed about the rigmarole to import a worker.
You can also try to go for a while as a Tier 4 student.
You got some advice on UK-Yankee, that's a site with very decent expertise in 'friends' of US/UK nationalities. Their answers will be the same as mine, but they have a forum format and this site is questions/answers. Given that you do not have a passport yet, it's really the best forum for you at the moment. We can help if something gets very technical.