Preparation is a must for monster houses. Everything else I would have to say on this subject others have already covered.
Idk about more recent PMD games, but in the first two games the main things you find in Monster Houses that have a low spawnrate anywhere else are Gummis. If you don't need Gummis or EXP, then I would probably avoid fighting monster houses unless you are overlevelled enough to not waste resources on them.
For those tough dungeons where you can't bring in any items to prepare yourself for monster houses (especially Zero Island South and Destiny Tower), it might be worth investing in grabbing Pass Scarf and/or a Warp Scarf. Either of the two makes escaping from Monster Houses almost trivial (Warp Scarf is especially helpful, but you need to survive for a couple of rounds first).
The Warp Scarf/Pass Scarf combo in general paired with a pokemon with good protection moves (eg. Lucario) makes you nearly untouchable in ZIS, but that's a cheese strat - If you want to experience the full challenge of the dungeon, you probably don't want either of those items.