What heaters/coolers would you recommend for renters / on a low budget?

What heaters/coolers would you recommend for renters / on a low budget?

Portable air conditioners are best for a single room, renters, or temporary situations. Since they must draw in warm air to replace the hot air they draw out through the duct, they’re only half as efficient. The duct should be vented outside necessitating on open window or door, which can let in heat or cold if not well sealed.

If you only require cooling a portable evaporative cooler might be suitable. 

A portable or pedestal fan is the cheapest form of cooling.