1. It won't create any problem when your employer runs your pay...............only problem will be you need to tell them that you will pay the Tax etc................it will be anywhere from $700 to $1200..........which you might be able to get back while filing Tax.....................run Pay for atleast 3 months

2. If your pay check nature is biweekly..........ie 2 checks/month then for 3 months you will have 6 pay checks so you should be fine in getting visa................but i would suggest you go for stamping only after having experience (or run pay check) for at least 6 months and 4-5 checks handy