A friend of mine told me 5k would be enough.

5k is same ballpark as one month of a senior developer (outside of USA, within USA it can be twice as much easily). 15 months and $5000 comes to a total of $330/month. Aka... I would rather work in McDonalds or supermarket. It actually pays better. Let alone when compared to actual programming or art jobs.

For 3 people working full time for 15 months if you wanted to pay yourself same salary as if you worked for an AA/AAA company you would need to make over 200k.

Catch is that making 200k $ with 3 people in 15 months is REALLY hard. It's a rule of scaling so to speak - if you have a budget of 2 million $ it's not that hard to turn that into 4 million $. If you have a budget of 10k $ it's extremely hard to make 10k $ back, let alone turn that into 20k $.