Your Viable options are
A.) Quick Flips - This is when you resell a domain fast for a low profit margin to another reseller and let them worry about finding end users.
B.) End User Flip - This is when you do the hours of research to locate the perfect end users that will pay a higher price for the domain. Note: Finding the right end user can sometimes take months or even years. This is a long hold decision that may require you pay renewal fee's till they sell.
C.) Quick Developed Flip - This is when you develop the domain into a website (unique or turnkey) and then sell it to a reseller for a low profit margin.
D.) Developed End user flip - This is when you develop a site, monetize it, add analytics tracking to it, Promote it for 3 - 6 months to build up the stats, then locate an end user to buy it that will pay more. This may take a while and sometimes you may end up having to pay renewals till you find the right end user to buy.
E.) Revenue Network - this is when you develop sites, cross promote them with each other, Monetize them to generate revenue, promote them, and keep them for yourself to generate reoccurring ad revenue each month.
No matter what you decide to do with your domains, there's always a way to make a profit off them if you do it right. Keep in mind that even if you are dealing with low profit quick sales, a profit is a profit and every sale adds up.