With the low interest rates today, maybe a little more. With today's low interest rates, probably a little less than one percent.
Lenders are extremely interested in the last two years.
One or two 30 day lates are probably ok, depending on your other factors. The lender can look as far back as 10 years. I'm self employed. Depends on your situation. If you are going to stay in the house less than 3 years or want to gamble on the future of interest rates, probably.