I can't choose...... breeding Guppies so I earn money so I can open for aquariums or a Betta?
Breeding guppies generally doesn't lead to earning money. What size tank?
10 gallon. If I go with Betta i'll get 3 ADF's @Littlebudda
You might be able to get some shell dwellers that will breed in that size tank and grown them out a bit and that would actually make you some money. Guppies are too common and easy to breed that they are worthless. But a 10 gal is limited with what you can have
In order to make money on livebearers, I had to have a 40 gallon to raise fry, and a couple of 20s for the adults. They need space and time to grow. A ten gallon will hold 3-4 guppies, and a store wants large lots that they will pay small money for. Aim for what gives you pleasure, not money. If in time you get larger tanks and more experience, then money can come. It won't with a 10 gallon.