You can get good seeds at Simlaw seeds or East African seeds. Most Agrovets will also have them in stock. You need to identify which variety of chilli you want to plant. It takes about 10-14 days for germination and roughly 2 months before you transplant from the nursery. Pesticides are used depending on the pest, but if your shamba is clean, free of weeds etc, you may not have to use much pesticides.
Try and find the market where you can sell before you plant. This will thus determine the variety and give you a start on selling, when you begin to harvest.