Heartworm Treatment For Trixie

As many of you know, we recently rescued our newest pup, Trixie. She is the absolute sweetest pup, and the best addition to our little family. But unfortunately her recent vet check up shows that she is HeartWorm Positive. I'm fortunate enough to work at a great animal hospital that offers a discount, but the cost for her treatment will be roughly $800+.  We aren't sure how severe the heartworms are yet, and will need Xrays before we can go through with the treatment. 
Heartworms can be fatal if left untreated, so we're hoping to get this started as soon as possible before it has the chance to get worst.
If you know me, you know I hate asking for help. But my dogs are my babies and right now I want to make sure I do everything I can to get this taken care of and get her healthy again. Thanks in advance, <3