If I had one billion, I would first do investment and make sure that I can live on the interest of it.

Then, I would engage myself in painting or my profession. 

Of course, having one billion also means I could donate my money to anything I would interested in, like Purasbar.

And of course wealth can ensure my academic career, freeing me from the fear of poverty.

Oh, that also means I can arrange my living on my own by renting / buying a house.