@Cole Leonida People sell off-market for various reasons: a relationship built over time, sellers trust the buyer will close (that actually means something, especially in this market where buyers are bidding beyond their means and can't get make the financing work), sellers have specific needs like moving, or problems they need solved immediately, etc.
What can you do to add value?: the biggest thing is whatever built that relationship in the first place. They know you, they like you, they trust you. The things you mention to make the transaction easier for them certainly help. Money certainly smooths over a lot of problems, but it's not everything that people are looking for. How do you find out what they are looking for and communicate this? This is a skill great realtors have: ask the right open-ended questions to find out what they're looking for.
At the same time, continue to be honest and up front with them. Know your terms: Will you have an inspection contingency or buy as-is? I never advise no inspection, but if it's new build, there may not be many issues, so you could have just an inspection termination deadline: You can terminate if there is a red flag, but they won't do additional repairs. (I often frame inspections as delayed maintenance.)
You may not get a "discount," but a fair market price in this fast-appreciating market may actually be less than the house would sell for if it were to go to market. Prices increase quickly in bidding wars.
You mention rent rates: have you looked at the market for mid-term rates (1-6 months), i.e. travel nurses, etc.? We're seeing an influx of remote workers who want to live in a cool place like Colorado and now have the work freedom to do so.