I'm confused by a number of things (perhaps partially b/c I utilize my own spreadsheet) so I'll just start firing away questions...
Is this property currently vacant? How long is your rehab going to take? Have you factored in carrying costs during your rehab? Are you doing this with none of your own cash (nice if you are)? If so, do your lenders know that, some may balk depending on other factors.
I notice the monthly income is about $650 more than it currently rents for- I hope that number is supported by comps in the area, and I'll assume it is.
How do you plan to pay back your investor? Using your pre-refi number after your interest only payment, you're making about $300/mo. After 18 months that's not even $5500, where's the other $20k coming from?
Your refi is for $90k, why? In order to pay back your investor if you don't have cash on hand your cash-out refi would need to be for $125k, not $90k.
The initial equity on the top of page 2 isn't correct- assuming your ARV is $160, your equity would be around $60k, not $85k.
Still looks like it could be a good deal, I'm just not understanding the assumptions in the spreadsheet.