I use a HIGH QUALITY 12 1/2' extension ladder that collapses down to about 30" high and fits in a basement compartment. I have used it for 6 years now and never had any problems with it being wobbly or having it collapsing while in use. Mine has a Type 1A rating and can handle 300 pounds. It is ANSI and OSHA approved and the current cost is about $250 at Home Depot. It is very sturdy and I used it to bring my motorized satellite dish to the top of my RV.
You can get these collapsible ladders with Type I and type II ratings which will lower the usable weight and the safety factor. I have seen the flimsy collapsible ladders for as cheap as $80.
One thing to remember with any straight ladder.....there is a label on the side that will show you the proper and safest angle to set the ladder. If the angle is too steep, you run the risk of it falling backward as you climb. If the angle is too shallow, you run the risk of overloading the ladder and it breaking. As with most things...follow the directions and keep within the specs and you will be fine.
Home Depot ladder