If you choose to work with SAG, you need to be aware of and follow their rules and regulations to the letter. There isn’t much flexibility when it comes to SAG contracts, and so hiring a Producer or AD who knows his/her way around a SAG contract will save you a lot of time and energy. The first time I ever hired a producer on a project was when I needed to work with SAG actors for the first time.
I didn’t know much about SAG contracts or SAG rules and regulations, and I needed someone who could file the paperwork and represent our film with the union because that wasn’t something I knew how to do, and I didn’t want to mess it up. Breaking SAG rules will get you fined, and understanding SAG rules will help you get accustomed faster to their way of working, so it’s something that I recommend wholeheartedly. Your alternative would be to make an ultra-low SAG short film on your own before taking the plunge into the world of feature filmmaking, thereby gaining some experience and getting yourself familiar with their rules.