TeamUp supports multiple payment methods (i.e. online credit card payments, Direct Debit payments, and offline/cash payments). You can specify which types payment can be made for different types of purchases.
For example, you may want all your recurring memberships to be via Direct Debit (to save money and decrease the likelihood of failed payments due to expired cards) but you might want to allow credit card payments for drop-ins and purchases of class packs. You might also want to allow people pay cash at your event or class for drop-ins but not for recurring membership payments.
You can change which payment methods can be used on your payments setting page (Settings>>Payment>>Manage Payment Methods>>Manage).
OR Settings>>Payment>>Edit if you already have a processor enabled.
Now you'll be presented with an options box where you can pick which purchases a given payment method can be used for.
For example, the below would allow a customer to use Cash to pay for all not recurring transactions such as sessions/events, courses and non-recurring memberships (class packs).