Also, I have the option of getting a co-signer but I am wondering if that will hurt my portfolio's credentials in terms of banks in the future?

She looked at FHA with 3.5% down and she didn't qualify without a co-signer because her tax returns only showed her making $20K after her deductions and expenses. 

What are some creative ways to find deals or increase what we can get approved for without needing a co-signer?

I’m not sure about other platforms, but Airbnb has a Co-Hosting option available. https://www.airbnb.com/help/article/1243/what-s-a-co-host Use someone you know or another local Airbnb host to manage your rental. 

Either on my own in the mortgage or with my husband a co-borrower. 

(I do make exceptions for collections issues in the event of short-term medical issues, where the tenant appears to be on the rebound, but would require a co-signer). 

First we try to make a request to the seller to add the investor as a 'co-buyer' on our original contract with the seller.

A co-worker of mine is starting a non-profit focused on senior and youth enrichment/activity programs.

But I doubt that, and is more likely that your niece, and your sister as a co-signer, didn't pay attention and read carefully the documents they agreed to and signed.I would say it's a bad way to start her rental history and risk a credit report stain because of cats, not to mention the trouble it will cause to the cosigner, if she chooses to just walk away.So, it looks these are the options:1.

In NYC where I am, if you got a CO for 4 units, you only get 4 meters.