Lethargic, uninterested in food

Hello all. My usually sweet, happy, energetic, food-motivated 10 1/2 year old cat Pin has not been himself for a couple of days. He has never had any major illnesses or injuries other than fleas a few times. For a couple of days he has been extremely lethargic. He usually will go wild in the night and get vocal and energetic around feeding time, but lately he has been sleeping all day and night. He has been uninterested in food (VERY out of character for him) but if I put him by his dish he will very slowly eat it and eventually finish and keeps it down (he eats Trader Joes Turkey & Gublets wet food, about 1 can per day). I checked his litter box and it seems like the normal amount and "consistency" of pee and poop for him; nothing out of the ordinary. There was a little dried poop chunk on the floor this morning but that's not uncommon from time to time. I can pick him up, gently pet/squeeze him to check for any pain or tenderness and he hasn't reacted negatively to any of that. Breathing sounds normal; eyes, ears, nose, mouth all look normal (best I can tell), no excessive vomiting... A couple of days ago he threw up a little bit of macaroni and cheese (As I mentioned he is very food-motivated so he will get into the trash sometimes) so maybe he got an upset stomach from all the heavy dairy. He also goes outside from time to time, so it's possible he picked sometime up from another cat or who knows what else...

Is there anything I can look for to determine if it's more than just a bug? Pin is a very brave cat so he could be in pain and just not expressing it. I know the answer is to take him to the vet but I'm currently unemployed and literally have no money right now. I'm afraid to keep waiting and the thought of him suffering in silence kills me, but I don't know what else to do at this point.

Thank you for any advice you can give...

I would bring him to a vet just to make sure he's ok.

Any change in behavior or food habits is a red flag and needs to be addressed by a vet.  Be sure he's drinking and try to get some food in him, even if it's just plain meat baby food (no onions or garlic or veggies) mixed with a bit of plain baby pedialyte.

What you describe could be so many things. There are so many reasons for a cat to be lethargic and have a loss of appetite, and even moreso because Pin goes outside. Pin is also considered a senior cat, and senior cats get senior problems. They can develop new conditions and diseases in their advanced age. I know it's not what you want to hear, but only a vet can help you determine what could be wrong with Pin.

Perhaps there is some information here that could be useful to you: http://www.thecatsite.com/t/155462/cant-afford-a-vet-please-read

I would suggest keeping Pin inside so that you can keep an eye on him.