Inspect, evaluate the structure compared to the engine you are planning on putting on it (and your flying skills).

If the box says .35 to .46 engine and you plan on sticking a .72 4-stroke on... better get out the glue and some materials to reinforce the structure. If it says .40 to .61 and you are going to stick a .46 on. the structure is probably OK.... just check to see if they glued it right. (because the Taiwaneese who glue em up dont fly em...)

If you make feather soft landings every time... no problem. If you tend to bounce it down the runway doing 16 "touch-n-goes" before it flops over on its back... its gonna break. (most of us are somewhere in between there...)

Generally, you have to improve on fuelproofing. Some ARF's you have to reglue a lot. Some ARFs you need just bolt things together and fly it.