How do I effectively underwrite properties?

[Tomás Gonzalez]

So I have no money. And found out about how easy wholesaling was perpetuated on youtube. So when presenting potential deals to investors that were not even under contract yet I would get that price rejected because the numbers didn't make sense to the investors and countered with something even lower. The new price that would be given to me by successful investors would be rejected by homeowners because the price was too low. What are some ways that underwriting techniques that successful people do? How do they know rehab cost estimates without wasting peoples time? How do you know which discount makes sense or what equation do you use for underwriting? Is it too late to start given that I may have fumbled many potential relationships in REIA? I really dont blame them either though. How does one do it? (I'm currently studying)