@Eric Dami Without knowing too much about the property, just from what you've said, my initial thoughts are this:
Is this a fix and flip or a BRRRR? If it's a BRRRR I'd recommend reconsidering granite countertops. Depending on the area for a fix and flip, I'd also consider cheaper alternative options to granite. Of course granite is nice, but if you're not going to be selling to upper-scale customers, or if the surrounding houses sell fine with no granite countertops, this might be an area where you could cut some costs and increase your margins.
As far as the AC unit and new heating go, your estimate of $9-10k seems a bit low to me. However, this is highly dependent on what is actually included in "new AC unit" and "new heating". If you're sticking an AC unit in a window and calling that a "new AC unit", that's one thing, but if you're completely redoing a central air system, you might be a bit low on your estimates. The same goes for heating. If you're replacing some piping, you may be okay, but if you're installing a new boiler (for example), you'll likely be too low on your costs.
Robert Leonard