Assume a 75' boat
will also have correspondingly tall masts. If height exceeds 65' MAX (and probably need to be less to clear some of the bridges) then you are very limited in where you can go. Basically close to the inlets and in the main port area wjch will not be cheap
One of the less expensive options, depending on your draft
is up the south fork of the New River. City of Ft Lauderdale rents slips alongside the river and if I recall
all the bridges between there and the port are opening so you don't have to worry about the mast
Another in Ft Lauderdale is to look for private homeowners that rent the slips behind their houses. One concern, very few of these allow liveaboards if that is an issue for you.
If you plan to list with a broker for sale
they can usually help find a slip but may want you to give them a central listing.