To Keep Or Not To Keep

I have recently developed several niche sites for sale and so far I have 6 brand new niche sites up and running. I already have the content for another few more sites but I haven’t purchase the domain name yet.

I am hesitating whether I should keep or sell those sites because of them have their pros and cons.

Sell now?
If I sell now, I can make about $80 – $200 per site depending on the niche and how I sell it. Not much money but that’s something if we’re selling 10 sites every month right?

Sell later?
I can sell them in another 6 or 8 months later after the site have been properly promoted and ranked for their targeted keywords and getting a certain amount of monthly income every month. If it’s earning about $50 per month from AdSense, I can sell it for $500 to $600, or any amount equivalent to its 10 months expected monthly income.

Keep it?
This one is a slow way of earning money but it will be a stable income source if I consistently promote those sites and getting targeted traffic on daily basis. If one site is earning at least $50 per month from AdSense, that means I will be earning $500 per month from 10 blogs.

Hmm.. what do you think I should do? Keep them or just sell them? Headache… and dilemma.