... Except me! Sorry I didn't get to this until today.
As already mentioned, you need to be sure there isn't any load where you want to cut. And as recommended, you can brace where you cut until you frame out the opening. FWIW, just yesterday, in S Philly, PA (near where I live), a wall in a 'corner store' collapsed. Apparently, the remodeling crew went 'beyond' the Permit they got, and knocked down a load-bearing wall. 2 people got killed - the foreman is in the hospital. One of the dead was having his store of 50 years remodeled for a 'new tenant' so he could retire. Well, the wife is a widow, and he's permanently retired.
Too many times on this Forum I worry about folks indescriminately knocking down walls or cutting joists (NOT in this case because the gentleman has the forethought to 'ask'. I commend that.) It never hurts to play it safe if you're NOT 100% sure of the load situation. My best to ya and hope this helps.