1. Database Size
Lets assume Bitcoin is now the standard peer-to-peer payment method. for Simplicity, let assume there will be 1,000,000,000 Transaction a day.
Visa's average sustained throughput is about 150 Million tx/day, according to Visa itself. So much for your first assumption. Do we want to be bigger than Visa? Of course we do. But let us start there.
Each transaction is approx 250b. (assuming there is only one input and one output). 41,666,666 6,250,000/ Hour or 6,944,444 1,041,667/10Mins
Average throughput is what is of concern here. Spikes can wait, as long as blocks are not persistently full. 37.5 GB/day, not 250 GB/day.
This will mean we need a min of 1.736GB 156MB blocksize to accommodate the transactions.
So...
Every Block: 1.736GB 156MB
Every Hour: 10.416GB 936MB
Every Day: 250GB 22.5GB
Every Year: 91,250GB 8.2TB
is added to the blockchain
[I'll leave the rest as an exercise for the reader]
So just to recap the above,
You would need to buy a machine capable of handling 1TB of RAM and possible a RAID Storage that can handle 91TB of Hard Drive Space
Yes, today the demands to be a fist-class citizen of the worldwide network of all money would seem to be daunting. Today. Tough titties. Sucks to be you.
It's as if you have never heard of Moore's 'Law', nor Nielsen's 'Law'. It is not as if we're going to displace Visa tomorrow, next week, next month, or next year. In the meantime, Blocapocalypse II will be here with the next FOMO spike.