​Converting a carport or garage can be an economical way of gaining extra room in your home. From my perspective however there are many issues this can create.
The concrete floor will not be moisture proof and damp issues will occur if another floor is not correctly installed.
You loose your car parking space, which can increase your car insurance premiums, as well as loose valuable storage areas.
The ceiling lining may now be an asbestos sheet, above where you have a bed positioned as any house built prior to 1985 would have asbestos sheeting used for the carport ceiling lining.
I do find a lot of wall moisture issues, mold issues etc in any converted carport wall. This then becomes a possible termite attractive zone, as the cladding is often over carport posts, that have inadequate or preventative pest treatment applied. The wall framework is often set down against the pathway or worse the driveway edge at ground level. This can enable moisture to wick up inside the framework providing the damp timber that attracts termites. 

​Winter and wet weather issues on a roof can be expensive to rectify especially if left not repaired.
Checking roof pipe penetrations and the lead flashing for cracking can often expose many areas of concern to be inspected inside the ceiling cavity. This roof for example, was be letting in enough water to cause serious damage wood rot of the ridge beam and rust out the nails it was supported to. The issue here was caused by cracked tiles.

Pipe penetration and lead flashing are the main cause of leaking into most roof cavities, closely followed by broken or damaged tiling and missing pointing