The definition of rescue:
Verb: Save (someone) from a dangerous or distressing situation.
Noun: An act of saving or being saved from danger or distress
Rescuing a betta (or any other animal that otherwise would have died) is rescue, regardless of whether you paid for him/her.
The only problem with paying for a betta that you have "rescued" is that it supports the abuse these lttle guys suffer at petstores.
However, even if you buy a healthy betta, you are supporting this.
And leaving a sick/dieing betta there does not make the store loose money, they are compensated for that lost normally
If you find a betta in a bad situation at a petstore, the best option is to find a manager and ask that you get a discount, if you are calm and polite, explain what is wrong with the fish and how it is going to cost you a lot to save himher (never hurts to mention you will have to buy a lot of stuff from said place to save him/her) the manager is almost ALWAYS willing to give you a discount or even a free fish
*I got my fish Hercules for free after he was placed in another bettas cup, he was torn up really bad
*I got Finn (a CT betta) for the price of a VT, he has NO fins left, so not the best deal, I really shoul have gotten him for free but I wasnt in the mood for arguing since I wanted to get him home
Hercules, Finn, Flagg, Sammy, Jackpot, Anchovy, Gotham, James, Honey, Echo, Ender, Merle, Orpheus, Dancer, Peanut, Dragon, Omen, Eurydice, Smudge
My FIRST spawn!!!!
Unknown number of fry... HM marble + HM marble
Ned, Lucky, and Dusty (AKA Nemo)
Chai, Punk, Pandora