There are a number of things that can be deal breakers for a large pool of potential customers and not having a bathtub in a home is certainly one of them.

Will,You don't need to know all of the code requirements for a specific area, but you do need to be able to tell the difference between a fuse box and breaker box.

Not having a bathtub would usually not be a deal breaker if you were to sell it.  

The electrical system has been tripping breakers.

That alone was a deal breaker.

Fully insurable title was a deal breaker for my develper client (understandably.)

If it has a fuse box instead of a breaker box, this will increase your premiums as will aluminum wiring. 

Lots of people think that non permitted extensions are a deal breaker and that you should always ask for permits on previous work but honestly that’s good for me because it scares people away and allows me to buy some really cool stuff.

Is this a deal breaker?

when at garage sales, I bring a book to read at appointments that run tardy or at the shop vs browsing my phone, I lift/do work before gym class starts vs just waiting by the door, I talk to the older folks after their senior circuit training, I listen to podcasts in bike class vs the same old music offered, I sweep up and clean up after myself on service calls and usually address something else while there, I smile and listen and am genuinely curious about the other person in conversations, I have no consumer debt or shiny new toys or gadgets, etc.