Why is my code looping for infinity? Here is the question prompt:

The credit plan at TidBit Computer Store specifies a $10\%$ down payment and an annual interest rate of $12\%.$ Monthly payments are $5\%$ of the listed purchase price, minus the down payment.

Write a program in the file tidbit.py that takes the purchase price as input. The program should display a table, with appropriate headers, of a payment schedule for the lifetime of the loan. Each row of the table should contain the following items:

the month number $($beginning with $1)$

the current total balance owed

the interest owed for that month

the amount of principal owed for that month

the payment for that month

the balance remaining after payment

The amount of interest for a month is equal to balance $*$ rate $/12.$ The amount of principal for a month is equal to the monthly payment minus the interest owed. $($LO: $3\mathrm{.}2,3\mathrm{.}3,3\mathrm{.}4)$

My code:

# Request the inputs and convert values

downPayment $=0\mathrm{.}10$

annualInterest $=0\mathrm{.}12$

paymentPercentage $=0\mathrm{.}05$

purchasePrice $=$ float$($input$("$Enter the purchase price: $"))$

#calculate starting, monthly interest, and payment

startingBalance $=$ purchasePrice $-($purchasePrice $*$ downPayment$)$

payment $=$ startingBalance $*$ paymentPercentage

interest $=$ annualInterest $/12$

month $=1$

#display the header

print$("\%7$s$\%18$s$\%17$s$\%18$s$\%9$s$\%16$s$"\%("$Month$",$ "Starting Balance", "Interest to Pay",

"Principal to Pay", "Payment", "Ending Balance"$))$

#compute and display results

while startingBalance $>0$:

if startingBalance $<$ payment:

principal $=$ startingBalance

payment $=$ startingBalance

interest $=0$

else:

interest $=$ startingBalance $*$ interest

principal $=$ payment $-$ interest

endingBalance $=$ startingBalance $-$ principal

print$("\%5$d$\%15\mathrm{.}2$f$\%16\mathrm{.}2$f$\%18\mathrm{.}2$f$\%14\mathrm{.}2$f$\%17\mathrm{.}2$f$"\%($month$,$ startingBalance,

interest, principal, payment, endingBalance$))$

startingBalance $=$ endingBalance

month $+=1$