Hi Mindy, I bought a cot and playmat when I was pregnant and simply because my spouse wants the baby to sleep in a cot instead of co-share our bed. When my baby was in the first 3 months, her movements are limited and having to keep an eye on her while I was doing housework, the playmat is ideal as I can move it anywhere I want it to be and much easier to move than a playpen.
When my baby reached 5 months, she started to turn on both sides and stretching her body and that's where we decided to let her sleep on the bed as it gives her more rooms to 'grow'. We didn't have to buy an extra bed as it is already available in the spare room. We put a couple of around my baby and constantly check on her to make sure that she does not fall out of the bed.