I built my house four months before. When should I paint my house? Some people say that I should paint it after one year. Is it true?

I live in hot old Arizona. The metal transition between my AC and the roof needs painting. Is there a paint that I can use to reflect the heat and keep the cooled air cooler, longer?

It was suggested that I spray or roll a waterproofing material on my T-111 siding before I paint. Will this make the new paint adhere good or will the paint tend to have less grip!