Like many other folks who spent a career in LE, I've had circumstances arise where I had to clear a small-to medium size structure myself. It's definitely not the preferred method. The advantage is not typically yours when you're the sole searcher.
Clearing a structure is best done at least as a 2-person team, at a minimum. Having a K9 available can be better, depending ...
Someone searching a structure, even if it's one with which the searching person is familiar, can easily place the searcher at a disadvantage. If nothing else, the searcher has to look, see and recognize any differences among the familiar environment, often under reduced/low light conditions ... while the person(s) being sought only have to react to incoming movement (against the still background) and/or noise.
Call 911 and let the folks who practice this sort of thing and are (hopefully) practiced in performing this sort of task together, do their thing.
Naturally, it's preferable, if at all possible, to not be inside the structure yourself as they do their thing. Unnecessary distractions and surprises occurring in elevated stress situations situations are best avoided, when possible.
Retired LE - firearms instructor & armorer