I've found a 5 bed, 3 ba with a completed walk-in basement which can be used as separate apartment. 

Very rare that you see bed frames in $650 duplexes and things of that nature.

Super relaxed city for STR as long as you pay the bed taxes. :) There are some neighborhoods and HOA's who impose restrictions- some successfully, some not so much. 

Check out this 7 bed 3 bath that we closed fairly recently. 100 years ago, they built 'em big and built 'em to last. 

She apparently passed away in bed, and it could have been up to 2 months before she was discovered.

I have the basics in each side already (bed, sheets, couch, table, light wall decor, along with all appliances).How much more should I add?

You normally charge rent for the real beds in the real bedrooms, and there is an extra bed or two in every house that you don't charge for if the real beds are all paying money. 

The purchase price was 98K for a 4 bed 3 bath sfh.

Your highest comp went for $205k when filtering at or below the subject property's beds, baths ,sq footage, year built and within a mile of the subject property. make sure you're not exceeding these figures while running your comps or you may not be an investor for long. the listing doesn't have interior photos which usually means there's a lot of rehab needing to be done.

I found a duplex (2 bed| 1.5bath| 1 car garage) in my area that I’d like to purchase.