Which is the best cat breed to afford ?

You go to a shelter and pick one that wants your attention.
- That's how I got my kitty! He climbed out of the kennel onto my shoulder and sat there like a parrot.

You want a domestic short haired cat. Easily found at any rescue or shelter. Comes in a variety of sizes and colors.

That one cutie of undefined breed from your local animal rescue.
- Two cuties*
  Always get cats in pairs. They tire themselves out instead of constantly needing attention from you

My parents always get purebred cats and I always get shelter cats. Without fail, my cats have been smarter, healthier, and more active than theirs. You can’t beat nature's evolutionary hand.
- My cat is a shelter cat, but she's as dumb as a post. But I love my little idiot.
- What breeds did your parents get? Out of curiosity.
  
  They’ve had several, but the derpiest are those flat faced ones.

Don’t get a pet if you aren’t able to handle it financially, including vet visits and an emergency fund

I don't know what the right term for a cat mutt is, but mutt animals that have a good diverse family tree tend to be pretty healthy. It is when the family tree starts looking like a telephone pole, there is a better chance of having health issues.
I'd just find a shelter baby that loves you. That is the best breed.

Also chiming in for the same reason...adopt a rescue, or better yet, adopt siblings from a rescued litter.

I have a pure bred Main Coon, and she came from a shelter. She has never been sick or had any health problems, she is 14 now. I agree with the folk here, adopt from a shelter or if you really like a particular breed, then there are specialised breed rescues. They rehome pure breeds ,but like many others already said they tend to have health problems though it differs from breed to breed just like in dogs. You really need to make your question more detailed. What are your living arrangements? Will it be an indoor cat or will it be able to go outside? Do you live in a city or are you rural? Do you want a very affectionate cat that is vocal, or prefer a more self-sufficient one? How many hours are you at home? Do you want a longhair or short hair? Do you have time to groom a long hair cat? Have you considered the cost of food, flea drops, wormer, vaccinations and holiday cover? Cats are wonderful and easy to live with.90% of the time you need to do nothing but the other 10% are important and if done well will make living with a cat a doddle.