Howdy! Noah here, new to Bigger Pockets. 
I just went under contract on a 35 unit apartment complex built in 1980 and I have to do some remodeling... YAY... Time to raise rents. 

I need all new appliances (Fridge,...

However, you can expect to recover about 50-55% of your investment when selling the home.Another good option would be to consider converting attic space, finishing a basement, or repurposing a large living area to add a bedroom without expanding the home's footprint.Some other tips to help you save on materials while still creating an appealing finished product: buy in bulk, shop at discount stores and outlets, look for overstock, discontinued items, or slightly imperfect materials, attend auctions and Estate sales, incorporate reclaimed wood, vintage fixtures, or other salvaged items for a unique look at a lower cost, build relationships with suppliers...If you have any more questions or are looking for funding please feel free to reach out to us, we're a private lender.Regards,Jackson

If your income isn't in a certain range or if you're not a real estate professional (amongst other items) the cost segregation might not be beneficial.

Since it's a duplex, it has one of some items (one roof?)

I own a small (72 unit) multi family in OKC and have seen vacancies go up and we have had to start increasing specials and extra items to attract quality residents to fill unit. 

You may have dodged a bullet if you really forgot to check and verify all the items.

I would recommend taking a  look at some of my previous posts which emphasize the action items you as a rental property owner should be implementing that have a far greater impact on asset protection than merely forming an LLC.

Any notes on NOT to do items would be helpful. 

Some have juiced that up too with all kind of party rental items. 

I was thinking I would create a course that involves a field trip to one of the flips I am working and pointing out all of the things they should catch and helping them understand rehab costs at a line item level.I am an expert in electrical and learned plumbing in the Coast Guard.