We are looking at lights/fans for the bathroom. We don't want to spend a lot of money. The fan/light combination units at Menards and Depot say to use incandescent or energy-efficient equivalent. The more expensive fixtures come with integrated LED lamps. The bottom line question is, can we use an LED bulb in the less expoensive fixture that says incandescent or equivalent?
Isherwood's comment is certainly valid, but here's a rundown of the possibilities (that I am aware of).
It has an Edison socket
That's one of these
It will likely be an E26, which is your standard light bulb size. Anything that fits will work fine (unless you find an incandescent that exceeds the wattage rating on the fixture).
It has an orange connector thingy
I don't actually know what they're called, but they look like this
Since these are mostly used in downlights (recessed lights) you can find LED trims for recessed lighting in the appropriate size (4", 6", etc.) for your vent fixture.
It has a built-in LED
You simply need to wire it. No replaceable bulbs are required.
You could find something that uses a GU10 or another type of bulb that isn't an Edison socket, but this category is largely the same as the Edison socket category. Simply find any matching bulb with wattage equal to or less than the rating.
Not 100% clear, but it sounds like you:
1 - Want to purchase a fan/light combo
2 - Would like to get a less expensive unit that uses a replaceable bulb instead of a more expensive unit with an integrated LED lamp
That is absolutely fine. I have replaced the incandescent bulbs in my own fan/light combination units over the years with compact fluorescent bulbs and more recently with LED bulbs. The wattage will not be an issue - typically these fixtures will allow up to 75W or 100W incandescent. An LED 100W equivalent will typically be in the range of 16W - 20W and a 60W equivalent even lower at 8W - 12W. Keep in mind that if the fixture has any kind of dimmer then you need to make sure that the fixture is compatible with LED bulbs and that the particular LED bulb is compatible with dimmers. But other than dimmers, no big concerns.
On the more general "bathroom fan/light installation" topic:
Generally the larger cost will not be the fixture but the installation. While I have done my own repairs, I got a professional electrician to do the original installation (and would do so again in the same situation, even though I have gained experience over the years since then) because the installation involved wiring through the attic (in my case I needed new wiring because I went from one switched device (fan) to 3 (fan, light, heat). If this is not replacing an existing fan (one of mine was, one was not) then you also have to consider work involved with installing the exhaust vent. So my recommendation is to consider an extra few $ (not too many) towards quieter and/or more powerful fan as you will NOT want to spend all over again if you decide it is too noisy or not powerful enough.