Is it sensible to set up a mining rig?

[LinkAkward]

Hello, I have a few questions for you about the mining rig that I have been wanting to build for a long time but haven't been able to do so. I'm looking forward to your suggestions.

First of all, I won't be assembling the system all at once, I will be gradually purchasing the parts and then starting the process.

Question 1: Can I use graphics cards from different brands in the system? Because either I will have to buy the same graphics card brand new or the assembly of this system will take much longer.

Question 2: Considering the current market, do you think it makes sense to perform this process? In terms of money spent and return on investment.

Question 3: Which application should I use for mining?