The more you learn, the more confident you will be. 

If you believe that what you are proposing is solid, your confidence will help sell it.  

Thanks to David Greene I feel more confident doing it

It was just what I needed to finally get serious about my real estate investing and now I have the confidence to say that I will complete my first real estate deal in 90 days. 

I feel confident that he did not do a back ground check on my tenants.

But, as you point out, it eventually will be in that 5th year, if your prediction holds true.So, if I were confident that $15K is the correct repair cost, and also that 5 years was the likely time-frame, then I would wisely set aside that $3K each year as an actual expense that would come out of income and go into a separate CAPEX account for accounting purposes.I would then adjust my NOI number accordingly and recalculate CoC.

He is, however, confident that he could get a renter at that price (though there may be a $50 discount incentive for a yearly lease which I would prefer due to less damage moving in and out).

Most importantly you need to convey confidence and assurance you are a player and not just wasting their time.

Without gaining a certain level of confidence, it will be tough for potential investors to get comfortable enough to invest.  

@Dave Foster ??