Is your income required to qualify for the loan? If your fiancÃ©â€™s income is sufficient you may be okay. If not, get back to work in the same field as quickly as possible. As Shane indicated if you are W2'd your chances are better. If you rely on commission or bonus income or become self employed this will be more complicated.
As far as time on the new job, you should just need to have received 1 paystub, but some lenders may want you to have a paystub reflecting you've received 30 days of pay. If the job gap is longer than 60 days, then you should be prepared to write a letter of explanation, but if your credit is good & debt to income ratio is in line then it still should be just fine. If your credit isn't so good, and your debt ratio is high, then after an absence longer than 60 days you may see some lenders wanting you to be on the new job for 6 months.
Sorry to hear about your job, hope you can find something new & better soon.