You save money by doing the repairs, but you lose time. There's also a learning curve. I would do the first fix and flip for the love of the game, know all the details so in the future your contractor can't screw you over, or if he's doing something fundamentally wrong you would know. That should be the point of doing it yourself, not saving money, because in the long run you are losing time, have vacant months and miss out on opportunities elsewhere.
There's complex stuff like single pane to double pane window replacement you always want to get the pro's for initially, or structural reinforcement if you're knocking down walls etc. But most of the stuff you can learn from youtube and the right amount of concentration/practice, and there's stuff I enjoy like anything related to woodwork/carpentry.
Do it yourself to learn the ins and outs and if you truly like it, but don't do it to save money. You're now an investor once you own, so you're losing time which is money.