Hey Brit.
I have to agree with everyone, this is very exciting and my first reaction is that you should go snatch him up immediately..
But, there are a lot of things to consider first. I don't want to discourage you whatsoever, because I think that you are ready for a new dog and so is Jackson! I just want to let you know how my experience has been, because I am around the same age as you.
My boys Marshall and Jimi got along almost instantly. They are both supersized yorkies and very active, so their personalities mesh well.
Most days they run around the house chasing each other, playing with toys, etc. They both love going for long walks together and from what I can see, they just enjoy each other's company.
Now that Jimi has a playmate, they keep themselves better occupied (so I have some free time to do homework and stuff when I am at home), and I also don't feel so bad when I have to leave them alone for extended periods of time - like when I have to work for 8 hours straight. They have really bonded - they sleep together, eat together, everything. If I take Marshall to the vet without Jimi, Jimi will cry by the window and watch us drive away..
I think that you will know immediately if Marco and Jackson will get along, once you go visit her house. It sounds like they have a lot in common, so hopefully they will love each other!
I know this depends on the dog, but are you ready for a possible personality change in Jackson? I know he is your baby so it is difficult to imagine, but when I added Marshall to my family, Jimi definitely changed. He used to be very submissive, but now he has more of an alpha male personality. It is not necessarily a bad thing, but he kind of puts Marshall in his place from time to time. I think he has a sort of understanding with him that he is the top dog.
It is also really important that you don't focus too much of your time, energy, love, etc. on the new dog. I think I spent too much time babying Marshall and I made Jimi feel threatened. Now whenever I pick up Marshall and not Jimi, then Jimi will bark or cry for me to pay attention to him. I feel bad for making him jealous. I don't know if this could possibly happen to Jackson, but I just wanted to make you aware of the possibility.
I know we discussed before that you wanted to adopt instead of purchase from a breeder, so I am a little surprised that you are going this route but I kind of have to agree with it. Although I would always recommend adopting, I must admit that it has been a challenge for me, especially considering factors like my age and financial situation. I feel great knowing that I rescued Marshall, but it has definitely been hard on my wallet. He only cost me an intial $150, but he has cost me several hundred more in the long run. Marshall came to me with an upper respiratory infection, and then he gave it to Jimi. That was just within the first week I had him. Since then, we have been back and forth to the vet, it is like Marshall's second home. He has all of this allergy issues and gets scabs on his body from itching, it is really difficult to deal with. So if you can get a healthy dog from a breeder, then I will definitely support you. Just make sure you review her vet records, and call the vet to verify that all of the information is correct.
Also, I want to add that I like the fact that he is already neutered. Hopefully that will help avoid marking and other unwanted territorial behaviors.
Last thing to consider.. Right now you are living at home, so you have an ideal living situation to add another dog. But- you said you are planning on moving/renting sometime in the future? Well, right now I am looking for apartments, and I must say that it is really hard to find cost efficient, dog friendly apartment, at least in my area. Most of the time there is an added security deposit, sometimes an extra monthly fee, and also they might have breed/weight restrictions. A lot of the apartments that I found only allow 1 dog, so right now I am kind of stuck. Most of the apartments close to my school, in my price range don't allow pets whatsoever.
I am a full-time student with a part time job, and with my small income I wouldn't be able to pay for an apartment on my own right now. You already have Jackson, so maybe this is something you have already looked into. I sense that neither you or I are in a big rush to move, but it is always something to consider..
I also didn't realize how much money I would spend on food for two dogs. I know you are well aware that it would 2x as much food, but once you get started with treats, harnesses, and all of the other things we love to spoil our babies with, it really starts to add up quickly!
I don't want to scare you away from getting another, I just want to remind you of some of the things that may happen when you do. Getting Marshall was one of the happiest times in my life. Looking back, I probably shouldn't have added him so hastily, because I wasn't really financially stable at the time, but I would never take it back. I absolutely love having two - they make my heart whole.
I hope you are happy with whatever decision you make. I know I had been pushing you to get another since the beginning.. (my fault, lol) I just hope that if you do get this little guy that Jackson and Marco love each other and everything works out for you!
Sorry this is so long - but if you ever need to chat, you can always PM me!
Good luck girl, keep us posted!