@basil-kezios - you can attach a quote, but there isn’t a custom field that will automatically insert a rate.
You’ll want to further define “rental amount”. Might be a good feature request, but if you’re in an inquiry phase, it would tricky to know which rate or total to include? If i have 5 different quotes, which one? I could see a custom field for reservation total, but would you want a field for just the rate before discounts, fees, and taxes?