Is there a certain time period you have to wait with no inquiries?
Does it really matter?
How many is too many?
Ideally you don't any within six months or so but in the grand scheme of things it doesn't really matter as long as your not taking on new debt. If you take on new debt right before apping that will look very bad. But opening up a card a few months that has a zero balance isn't a big deal. I opened an Amex two months before apping and they didn't say a word. I did have to write a LOE for every inquiry for the last twelve months. Mainly what they are looking for are accounts that you may have opened that aren't on your credit report.
I opened a BOA credit card a month before applying. I didn't think our house would sell so quickly so I was not planning to apply for a mortgage only a few weeks later.
I had to write a LOE for the new card. I also am making sure not to use it and leave at zero balance through the process.