if it’s not your usual bag it’s kinda hard. if you’ve done similar stuff on a smaller scale in the past then at least you base some of it one that.
If it were me I’d give maybe a ball park but do the work by the hour ( time and material)
You could gestimate your time and pad it, if he wants to pin you down for a price. but be careful, those kind of jobs can easily take longer than you think.
What those “termite dudes ” get for a thing like that may have very little to do with what the job is worth to you.