To get a spouse visa, your fiance will need to be earning at least £18,600 a year, with a suitable home for you both to live in.
If you qualify for a spouse visa, and once you've been living in the UK for 6 years, you can look at applying for ILR then citizenship. You don't get to be a citizen just because you marry one.
As an American citizen you can visit the UK for up to 6 months visa free, you will never get a spousal visa or citizenship of the UK unless he is living/working in the UK earning at least £18,600, has a home and sponsors you and then you would have to live there for several years before you could apply and pay for citizenship
You need to do this one step at a time. First complete the US process. That means you get married and you then sponsor him for a temporary and then permanent greencard. Once he has held his greencard for three years, he can apply for US citizenship.
At that point you can consider moving to the UK and doing the same thing the other way around. UK sponsorship rules are stricter than those in the US because he will need to personally earn enough, no co-sponsorships are permitted.
You can switch around and do the UK first. You cannot do the two processes in parallel because the sponsor needs to be resident and working in the country. They ask for tax returns.
Hi Ashley,
The K-1 visa has a single requirement: that the beneficiary, your fiance, and you get married within 90 days following his arrival in the United States. Thereafter you two will file for Adjustment of Status (AoS) which costs $1,060 and takes anywhere from 3 to 5 months. Once AoS is approved, your husband will get his conditional, 2-year Green Card. Within the 90 days before that expires, you two will file for Removal of Conditions, which is a pretty big deal. Once that is approved, he'll receive his unconditional 10-year Green Card. But even then, he would have to permanently reside in the United States, so while he can visit the UK once in a while, he can't live there anymore, can't reestablish residency, can't work there.
You, as a US citizen, can visit the UK visa free for up to 6 months, so you can join him when he visits friends and family during his limited vacation days or over the holidays.
Your then husband would have to naturalize, become a US citizen, before he could come and go freely. That's really to far in the past to even discuss now. Only afterward he could move back to the UK, establish residency, and a year later he could petition for your immigration to the UK. And from that moment on everything would be returned, as you would go through the spousal visa, ILR (equivalent of a Green Card), and eventually naturalization process. By then the UK may not be a country you want to visit anymore, given the enormous influx of immigrants from Muslim countries.
參考: An immigrant from Europe, I live on the American Rivera and work as an attorney in Santa Barbara, California.