laurak93

Hello Laura--The first part of the process (your petition) is the same for everybody. There is no proof of income for that. You only have to prove you--
1) are a US citizen
2) are free to marry
3) intend to marry your fiancé within 90 days of his entry on a K1 visa
4) have met each other in person, face to face during the last two years.
It doesn't matter if you live with the folks, have a job, fiancé has a job, etc. They are only evaluating if your fiancé will be allow to actually apply for a visa. The second part happens in London where he applies for a visa, and is vetted on his police record, medical condition, and having a financial sponsor to convince them he will not become a public charge in the US. (Very simplified, but I wanted to separate the two parts for you,)
When your petition is approved, the case ends up in London. Each consulate has their own procedures for for that part of the process. I am going to explain what is acceptable for London.
Your Dad can be a sponsor if you wish. It is about his income. They do not look into credit reports, bankruptcy, etc. He would fill in an I-134 and you wouldn't even have to do one. (It's a London thing.) it does not matter if you live with Dad or apart. Not a concern.
London allows self sponsoring. If he went to his interview with his financial statements showing he had $30,000, they would probably pass him right through with no I-134 from anybody. There is no published amount of what passes and what won't.
If he went to the interview with an I-134 from you showing $10,000 income and his financial documents showing his $30,000 cash, they would probably pass him right through. It doesn't have to be all in your pocket. There is nothing written in the law that is specific for the K1 visa support. It says the officer has to be convinced your fiancé will not become a public charge. London is pretty flexible.
If you have full time work and a new job with a good salary, a letter from your employer stating your salary would be enough to convince them. They do not require a tax return showing you made enough the previous year. Also they can approve a fiancé who makes only 100% of the poverty guidelines. (If your Dad sponsors, they will look for 125%)
Again, this is LONDON information and does not apply to other consulates. And it applies to the Support form I-134 for a fiancé visa. Once he enters the US and you marry, he will apply for a greencard. There is another support form I-864 that you must fill out with stricter and more specific rules outlined in immigration law. Yes you and Dad both would fill out a form if he co-sponsors. Yes, you must send in a tax return. Yes to 125% of the poverty level for you or enough assets (savings) to supplement the shortfall in salary or a joint-sponsor. Yes your husband's savings can count. That form is also doable for you. I just wanted to point out that it is the one with stricter rules. The visa one in London is not so hard.