The down side to getting wood off tree surgeons, or taking a chainsaw to a neighbours felled tree, is that the wood will usually be wet. This means you have to have somewhere to store it where it can be air dried. This may take any time up to a couple of years, and the outcome cannot be guaranteed. I’ve tried it with cherry and eucalyptus. I rough turned the cherry into several bowls, but they distorted so much as they dried, that I only got two reasonable bowls out of them. Similarly, the eucalyptus developed massive splits that made the wood unusable.
Personally, I prefer to pay a bit extra for blanks that I know I will be able to turn straight away, and not have the faff of having to store and dry.
Each to their own, I suppose.
D.