Ok. Here's my 2-cents.
1. The best deals never make it to the Zillows, MLS, etc. I work very hard to "get lucky" once or twice a year. And if I'm looking for someone to "bring me a deal" I have to ask what's in it for them. Why should they offer me a great deal instead of the x number of investors they have been working with for years.
2. You're right about making sure the first one doesn't loose money and hopefully makes some with cash flow and on the resale.
3. I've done well enough over the last 25 years with putting my emphasis on cash flow (I wanted the income more than appreciation) and minimizing leverage ( bumps in income/corrections along the way have not harmed me with loss of properties or standard of living).
4. I was never a calculator of potential but more of a do the numbers work in worse case scenarios.
5. I try to detach emotionally from a deal or least stay committed to my "do the numbers work" spreadsheet which gives me everything I need to know on one sheet of paper. No future appreciation enters my calculations with buy and hold.(That may or may not be a bonus)
6. I Don't get greedy unless the deal allows it. I don't make up "what if's" to "make" a deal work.
7. I don't follow the "stupid money" where things are bought and sold at non-sustainable values and manipulating the next person into paying more than it's worth before they catch on to the reality of what it's really worth. Corrections have periodically killed that group although there is money to be made if your timing is right. I'm not good at that and respect my weaknesses and focus on my strengths.
Best of luck.