In terms of framework, I tried to do what I thought was right, which was to make sure the company I was working at could fend for itself. Being more selfish would have helped, but I shouldn't tread that path...
I've yet to find a definition for true success.
Defining success can be hard. Do you at least know if success is related to profitability, valuation, and/or target industry? For example, I know success for me is if the startup is profitable regardless of funding but needs to be in an industry that I don't find distasteful. For example, I would find it distasteful if I was making profit from selling payday loans.
By the way, what do you mean by the company must be able to fend for itself? Does that mean the startup has to have a patent or is addressing a market problem in an industry with high barriers of entry (government, defense, healthcare, etc) before you join as a co-founder?
In any case, you could include within your framework any of the below ideas:
>Interest in the startup idea
>Type of co-founder
>Amicability of the co-founder