How can I create a currency field with thousand seperators

$125,000

I have checked your form named "Sun American MPR" and cloned it on my side in order to investigate it.

As far as I see, you need to receive some payment information for the mortgage. Let me suggest you using Form Calculation widget for the "Mortage Amount" field because you are able to decide trailing zeros as seen below:

After, I have added a number field and set 125 by default as seen below:

After, I have set that number field to the calculation configurations as seen below:

So, in the publish mode of the form, it will be shown as seen below:

Please find the form URL on my side in order to see: https://form.jotform.com/73022009723951 

Moreover, you are able to receive that payment via payment gateways on the form. To learn more about setting up the payment integrations, you can start with these guides:

https://www.jotform.com/help/47-Order-Form-Basics 

https://www.jotform.com/help/49-Order-Form-Types 

https://www.jotform.com/help/165-Setting-Up-Your-First-Order-Form 

https://www.jotform.com/help/323-Mastering-Payment-Form-Integrations-with-JotForm

I hope this helps. Please tell us if you need any further assistance.