Tenants will pay all CAM, and I can even try to bill them a portion of the property taxes.

Become a subject matter expert for the portion of real estate investing you're interested in.Focus on what you can change/control, and the rest will follow.

I am afraid I won't get even close to a portion of the amount I need for cash out if I refinance. 

The house is in good condition, ~ 20 years old, and but in a quiet suburb (20 minutes away from some major attractions).Here are the questions:- I can afford to buy my sister's portion but can I / should I put a mortgage down on her side?

@Joey Allison Just curious, how did you come up with a value for your portion. 

Should I return a portion of the deposit of the roommate leaving?

I’m about to do a rehab in Ridgewood and the median price there is 707,000, location is vitally important. 

It could use some shrubs to make it more inviting (pic with the pitched portion of your roof in the right side).

I would however add that if you can come to an agreement on damages during the walkthrough you can document that and return whatever applicable portion of the deposit to them immediately.

You won't "save" the property tax portion because it still has to be paid.