Offer accepted/did I offer too much/cold feet

[Zachary Lowe]

All input is appreciated.

I have finally after long years of analysis paralysis  had an offer accepted on a 14 unit.  The seller has agreed to seller financing for a time but now I'm concerned I've offered too much and have no exit strategy. Outline of the deal:

Asking price: 495k

Offer( after back and forths): 360k @ 5% interest only for 36 months seller financing, zero down (offer accepted)

Annual Gross: Potential: 67,260 / Actual: 59,000

NOI: 37,000

Contract was drafted by realtor for me to sign today however I noticed a few errors and declined.  Realtor should be drafting new contract today.

I'm the mean time I've convinced myself I've offered too much. The property is a solid B with long term tenants, low vacancy, new roof.  How comfortable would you be in being able to obtain a cashout refinance to cover the proposed 36 month balloon? 

Do think I've done well, if not how would you approach trying to lower your offer after verbally agreeing on it?

Any and all feedback is most welcome.