Hey there!
First off, you stated you wanted to start a "Non for profit Gerbil breeding project". I suppose my next question here would be..."Why?"
If you are going for NON Profit, then I suppose I cannot understand why you would desire to breed gerbils unless there is that high of demand in your area for them.
Then later in your post you said " Once SOLD.."
Selling indicates profit.
And honestly, to be fair, animals should be sold for some amount of reasonable price as I feel this gives the owner incentive to care for the pet because they have a monetary investment involved in the animal. People tend to take care of, more often than not, things they spend the money to get.
You need to be aware, there isn't a lot of money to be made in the breeding and selling gerbils, in fact, many times its more of a financial loss.
This is not a reason to breed.
Second, Are you new to gerbils? Have you researched anything about their breeding at all?
There are several things wrong with your ideas here regarding them and, no offense, but its a bit alarming, careless, and reckless.
I'm sorry. Breeding any animal is a labor of love, not a "project" -- unless your a Scientist and I assure you, there are plenty working with gerbils already.
One - you cannot simply remove a male an female and just "place them together" in a "large bin and watch them breed."
Always, always you have to pick gerbils based on health, genetics, and temperament before ANYthing else.
Then you always, always, have to go through the Split Cage process in order to get adult gerbils together, even opposite sexes.
Sure, sometimes its love at first sight and the male and female are eager to get together quickly, but on the flip side, females are picky, and may not be so keen to accept the chosen male and needs some convincing. Females rule the roost in gerbil society and many times it takes a careful hand in getting pairs together otherwise, your going to have some nasty, bloody fights on your hands and 10 to 1, the males are the ones that get hurt.
Gerbils also, don't always mate right away. Sometimes it takes a few days to a week or longer, for them to actually breed.
Also, you.. realize Gerbils are a species that mate for life? Constantly ripping breeding pairs continuously apart can have an impact on their mental health.
And then there is the issue of leaving the mother alone to raise the litter herself. Yes, where you can do that and many times the mother is fine raising the litter alone, this is always best done leaving the male with her to help with her first litter and letting them have a second litter. This way, if you must remove the male, then you can leave a daughter with the mother to help her raise the 2nd litter and it will never be necessary to leave her alone to raise one alone.
And, there are times, where mothers left alone to raise a litter will simply not raise them and end up neglecting them for whatever reason and sometimes, worse, harming and killing them.
Swapping the mother and litter between tanks can be very unsettling and confusing for the mother.
It is important to leave as much familiar and the same as possible when the mother is tending to young.
Last but not least, you mentioned "placing the sisters back in and the cycle starts again." If your planning to return the mother back to her sisters, AGAIN it isn't just as easy as that.
Especially with splitting up a three some of related females. If you are not, then you eventually will have three females split up, each preferably with a daughter, in three different tanks.
Effectively doubling what you have now.
Also, you realize you can never breed the pups together as you have three related females. All their pups will end up related to each other on the mothers' sides.
This will cause an Inbreeding situation.
All in all, coming from the opinion of another breeder, this simply is NOT the way to breed and, with all due respect, I encourage you to please reconsider your "project" and your reasons for breeding in general.
