So an example would be a secured private loan, (secured by real estate a 2nd position on a property or properties), with a 15 year balloon, interest only.

When I wrote to them about it, they responded: "Our Opportunity Fund is filed pursuant to Regulation D of the Securities Act, which requires investors to be accredited." 

May be look into tax exempt securities such as municipal bonds or series EE. 

I meet them and sign the lease and collect security deposit.

As you are house hacking I can see your concern, however, you need to have the business mindset and assess if their filth is causing actual damage that will in turn cost you more money than their security deposit or vacancy time as you clean it up.

I’m a new investor trying to secure my first property that I then plan to rehab and sell.

Several weeks ago a friend of mine and I decided to begin our real estate journey.What are the pros and cons associated with the following paths towards securing financing? 

I've contacted insurance and secured the home, however, I've been getting many calls from "Public Adjusters."

You can't see a hole in the wall from your phone but you can ask what the rents are or who has a security deposit

The lender is looking at the underlying asset (property securing the loan).