Knowing what the loan officer is going to look at makes the call shorter and the answer more useful. There are four things, and you can estimate three of them before anyone picks up the phone.
1. Your equity
Your home's value minus everything you owe on it. The lender will confirm the value with an appraisal or an automated valuation, but your own estimate is a good start.
2. Combined loan-to-value
Everything you would owe after the new loan, divided by the home's value. Most lenders cap this around 80–85%. That cap, not your total equity, sets how much you can borrow.
3. Credit
Higher scores get better rates and higher limits. Nothing on this site involves a credit check. A lending partner will tell you when and how they check credit if you apply.
4. Income and debt
The lender wants to see that the new payment fits alongside everything else you pay. Have a rough idea of your monthly income and your other monthly debts.