With Netflix, their value proposition is:
- Simplicity - it's very simple to select a movie on their website, and you can spare a walk to a DVD rental shop/supermarket. It's even easier to stream a movie.
- Price. $10/month is much cheaper than $15/DVD, if I watch several movies a month and don't plan to re-watch same movies very often
I don't see how that's applicable to the remove development - price argument doesn't work (it's actually cheaper to own an old Mac in the long run) and simplicity could work both ways - it's easier to start with remote development but having a local GUI development is probably easier.
Re: your decision to buy or not to buy a Mac - I just wanted to highlight that on the grand scheme of things - where you want to invest your time, which is your most valuable asset - decision to buy an old mac is an easy one to make.