I know you have received all the advice you need, but I wanted to give you my perspective based on first-hand experience.
I was a single mother, working long hours, waking up at 4:30 in the morning to get ready for work; so starting from about the time her sleep habits changed, when she could roll over, it was just easier for me to lie down with my daughter to get her to sleep. Inevitibly, I would fall asleep next to her. I would wake up around 1:30 and take a shower. In fact, "wet" was one of my daughter's first words in English. She would wake up, feel my hair was wet, and say, "wet."
I did eventually ween her into her own bed with a lot of pain and suffering for us both, but due to numerous reasons, (we moved back to the States and stayed with my folks for a few months where we shared a room; we then traveled and had to share a room; she has asthma and sometimes has very distressed breathing at night; etc.) so she is back in my bed.
I love sleeping with my child. On the rare occasions when I don't sleep with her, I miss her. But I never have a moment alone. I get up, get her ready for school, drop her off, go to work, leave work, pick her up, get her ready for bed, and go to sleep with her. Most or at least many weekends I try to fill her days as much as I can, and the added benefit is that she often falls asleep on the way home and is out for the night. Those times I find myself staying up just for the sake of having some alone time. (Sounds really pitiful now that I put it in black and white.)
My daughter did and still does reach developmental milestones very early. I attribute some of that to the fact that I carried her in the front carrier for hours a day until she was 8 months old, and that I slept with her.
But based on my experience, I would advise everyone to put their child to sleep alone. My sister did it with her second child. We had both moved back to the States at the same time and were all living with our folks when she started putting him down at 6 weeks and letting him cry until he went to sleep. The first night it took nearly an hour. The second night about 10 minutes, and then within a couple of days, he would just go to sleep without crying. (We both were kicking ourselves that we hadn't done that, me with mine and her with her first son.)
He is a much happier child than his older brother, though I know that is mostly just personality. He also speaks very clearly for a 3yo, has the vocab of a 5yo, knows every song ever sung at his daycare, his ABCs, can count to 20, and knows the pledge of allegience.
I would advise putting the child to sleep alone ASAP. The older they get, the harder it will be, and with the new child coming . . .
You need alone time, and I think the child does as well. Fortunately, it is my daughter's personality to be independent, but I think she has developed dependence on me she would not have if she didn't sleep with me.