One...all new cots should conform to safety standard BSEN716, which determines such features as the gaps between bars and base depth. So check your new cot's design is covered by this legislation.
Two...If buying a second-hand cot or inheriting a family heirloom, check for old paints that could include harmful products. If in doubt get the cot stripped and start again with a modern, child-friendly finish. Older cots may not conform to British Standard guidelines but that doesn't mean they shouldn't be considered...find out about the cot's history, you may find several grown-ups slept soundly in it as babies..!
amberinteriors via ministyleblog
Three...Whatever your decision, make sure you can get a brand-new mattress to fit your cot...it needs to fit snuggly with no gaps that little hands or faces can get trapped in.
Now, I'm no expert and these tips are, by no means, the only things to consider in the circumstances...
whatever you decide, take your time and seek professional advice from those you trust...