T.B.
We bought a white convertible crib for our first (now 3) and used it as a crib, then toddler bed. It was perfect to transition her into her big girl bed. She only used it from about 20 months old until about 23 months old when we moved her into her big girl bed because little brother was going to be born. (We moved her about 6 weeks before he came so that she would be "set" with her new bed and not associate losing her other bed with his arrival.) Since our boy (1 tomorrow!) is our last, he may end up using the toddler bed a bit longer, we'll see.
This worked for us! I guess it might depend on how close together you plan on having your second as to whether you can get away with using the crib/convertible.
BTW ~ we didn't buy a toddler bed for our daughter, she went into a twin bed at 23 months. The salesman suggested getting a "bunkie board" instead of a boxspring. So she is only sleeping on a twin bed frame with a board and a mattress. This meant she was closer to the floor in case she rolled out of bed (which she never did). It was easier for her to get into (and out of) by herself and comforting for us to know she'd be safe. She's 3 now and tall, and we're probably almost ready to go buy a boxspring to add to her bed. Of course, this stage will be a ways off for you, but it was a great tip for us from our furniture salesman! (It saved us a bit of $ at the purchase and this furniture could last her until she moves out of the house! LOL)
T. B, 39
Mom to Katelyn, 3 and Matthew turns 1 tomorrow!