One coat Zinnser 123, pole sand the walls with 150 grit and apply 1 coat of SW Superpaint Satin Exterior. Don't over buy on the finish coat as the 123 will seal the walls. Wait until SW is having a sale or use a contractor's discount.
First off, you're not going to get a professional job because you're not well......a professional - no offense. Your best plan would be to get a reference from a paint supplier (not a big box store) and tell them about your budget, your willingness to help and hopefully they can find you a...