Triib allows members to pay for a membership by cash.
To process a payment for a membership being paid for with cash, navigate to the member's profile > select the Payments tab > select View Details for the appropriate invoice > select the orange Mark Invoice as Paid button.
NOTE: if the member has put in a credit card or bank account information, the default payment method will be the credit card or bank account. You will need to manually change it to cash if they want the membership plan to be paid for by cash every month. Go to the member's profile page, click edit member information and change the "Default Payment Method" to cash.
If you would like members to sign up online and pay later then, make sure to "allow Online Signup Without Credit Card" when creating the membership plan.
Memberships > Add Membership Plan, check the box "allow online signup without a credit card"