Thank you all so much for your suggestions!
@grossidm, you mention that I will outgrow the D5500 too quickly, and that's actually a concern I've had. In fact, my first choice in an APS-C DSLR was a D500 as you suggested. However, as I've read and watched Youtubes for several months, it seemed on the subject of Nikon beginners that a lot of more experienced photographers and professionals recommended starting with simpler cameras, and the D5xxx and D7xxx series have come up often. Of those, the used D5500 was less expensive, and therefore less loss when I moved up to a bigger, better model! So that was my thinking anyway...
@Charles Loy I've also looked really hard at that D7500, thinking that eventually the higher fps and the buffer size might be better for my wildlife aspiriations, and it was getting me closer to that D500.
@bleirer, I have really had fun shooting with the P900, and my little Canon point and shoot has given me great, beautiful photos as well. My reasons for moving into interchangeable lens cameras...I think alot of it is challenging myself more, and that I might eventually be able to get higher quality shots. It definitely gives me joy when I feel that I've captured a moment that I can share with friends. I wouldn't mind investing more as I go, if I truly enjoy the challenges and it results in higher quality photos. I appreciate you pointing out the need to budget for all the necessary accessories. I've been comparing some straps (better than the ones that come with the cameras) and camera bags...I have the computer with the card reader...like any hobby, I know there is always
more stuff!
@jeffnles1 - thank you for the suggestion of giving the Sony consideration, I will give it a look. That fall your wife took with the P900 extended - the fall is terrible in itself, but breaking the camera to boot! Double Ugh! I nearly dropped mine while taking photos of the partial lunar eclipse in November, and I had to take several deep breaths before I could resume.
@Craig Yuill - Thank you for the mirrorless recommendations, I've read really good reviews. I've also had a friend recommend the micro four thirds cameras for the sake of lighter weight, and read good things about those.
@Warren D - thank you for your starter kit/lens recommendations. I'll look at these as well. Ditto
@Abinoone - I appreciate the starter kit suggestions and also the reading material. I am going to look at the Peterson book(s) on Amazon.
I am overwhelmed with the responses from all of you, and appreciate you taking the time to give me all these suggestions and sharing your thoughts. It means alot, and I will definitely take it all to heart. I have a tendency to overthink things, but in this instance I think it's best to give it plenty of thought! thanks again to all of you for your time and sharing your knowledge.