This is tough one, and there's no right or wrong answer that applies to all cases. My take on this subject is as follows. I absolutely would not bring another cat home if I wasn't 100% sure I could cover the most potentially expensive complication without detriment to the quality of care I provide for my clowder as a whole. That is to say, the means I have currently enable me to provide what I deem a quality life (good quality food, litter, and essentials) for my cats and I am not willing to potentially compromise this ability by adding another.
That being said, I'm trying to envision myself in your (OP's) situation, and I don't think visiting the neighbor cat, pet-sitting, or even fostering would satisfy my want of feline love, although these would certainly help. It is clear to me that you are looking for something more:
I want a cat that is at least a year to see his/her personality. I want a love bug. I want a cat that's loves to be held and kissed and let's me dress him/her for halloween and christmas. I want one that greets me at the door. I guess i'm saying i want one that is perfect for me but i know that is not reality. I feel alone without a cat.
OP wants to come home to a cat. I completely understand feeling this way. On horrible days, sometimes the thought of seeing my fluffs after it all is one of the most soothing. Their companionship has been a huge net good in my life, as I generally don't do so hot with extended solitude.
So, my advice would be twofold. I would start saving. Set aside a little extra each month or week, and make a habit of it. Every little bit helps. Make it the 'Cat Fund' for emergencies. OP, you cared for two kitties for years, so I assume the day to day expenses aren't the problem here, but rather, the potential expense of emergency care. You might have to pinch pennies, but it will be worth it knowing you can take care of your future kitty. Nothing would be worse than seeing him or her in pain and not being able to help. Second, I would definitely start volunteering a shelter, maybe two to get a feel for them. Put in some good hours, get to know the staff. Everyone at my shelter is wonderful, and super friendly! Explain to them your situation. They may be willing to provide for some of the potential emergency expense given that you are a low income senior living alone. I think this is quite reasonable. To this end, they may be willing to assign you a cat to care for as a long term foster home, if they won't acquiesce to adoption given your financial situation.
I really hope this helps and that you figure something out soon
I know how awful it can be to feel lonely, it's not fun.