Hey dude! went through a similar situation. Had a great relationship with them (startup), never doubt their word, the product was landing clients and valuation was awesome. Things didn't go as expected. Still have my business though it has come out damaged.
What I've learned: Don't ignore the signs, I never got to know why the previous developer dropped out. Ensure that you have a voice in every decision. Work with them, get to know them through rough times. Go over their metrics, are the clients really happy, is there any structural issue? Startups bullshit all the time.
Don't take any decision under pressure. If you have too, make them sign a contract that would protect you and you're current assets, that's what you're bringing into this enterprise.
What I've learned: Don't ignore the signs, I never got to know why the previous developer dropped out. Ensure that you have a voice in every decision. Work with them, get to know them through rough times. Go over their metrics, are the clients really happy, is there any structural issue? Startups bullshit all the time.
Don't take any decision under pressure. If you have too, make them sign a contract that would protect you and you're current assets, that's what you're bringing into this enterprise.