The amount of money you can earn with 50,000 monthly unique visitors will depend on how you make that money.
If you're using adsense you might make around $100.00 to $150.00 per month from the adsense revenue depending on the cost of each ad click and your click through rate.
If you're selling E books or promoting affiliate offers you might earn $300.00 to $500.00 per month.
If you're using adsense and want to make a good income of around $100.00 per day you'll likely need 6,000 to 15,000 daily unique visitors depending on the niche your website is in.
Some adsense clicks pay much higher than others in certain niches.