I just purchased my first rental property and I'm wondering what apps or software you use to keep track of the incoming rent, along with expenses of taxes, insurance and repairs?

Once you use the money to fund a project you'll want to know what fees you might be paying when you write a check.DM if you have questions.

Also worth a mention she has planned a hdhp hsa plan and I believe that would be even more tax write off for me as well?

Just reference the loan number if you write a check but almost every bank will take auto-payment too.Leaving the House - get a will! 

I would seriously sit down and look at "what is the minimum we can do to get this into a sell-able condition".Sell-able doesn't mean "looks great and tenants/buyers will love it", it means "a buyer will walk through and think, this can be rented at roughly market rent", and won't think, "man this is a fixer upper I'm gonna need to dump money into to make it rentable".Multis are, as I write this, still pretty hot.

Get everything in writing, on their letterhead.

You can also use software like ours to find all of their other deals, then look at the history of those.

The liability exposure is going to be different as a landlord and as an owner/occupant, so as @George Skidis said, you're going to need to get a commercial policy to write the coverage as a landlord, and then get a renter's policy to cover your own property and liability. 

EVERYTHING in writing .  

That means you would follow the same steps as above to establish the same protection of a LLC for Sibling #1 and yourself - then writing an Operating Agreement that would once again state how you two would want to operate this property now and into the future.