Ad layout in A5 landscape booklet and production of a print-ready pdf

I'm looking to produce a monthly A5 booklet in landscape orientation, which will be advertising local businesses. Your job will be to layout the adverts in this booklet – according to a specific design brief – to create a print-ready pdf, which can be sent to the printers. The booklet will contain 4 different advertising spaces: double page spread, single page, half page and third of a page. Each space will comprise an advert. In the double page spreads the advert will comprise the entire left hand page, with three separate mini ads on the opposing page. In the vast majority of cases, the adverts will be designed already. As part of the brief, I will let you know which advert will go where within the booklet. Since most of the adverts will be already designed, I will either send you a scanned copy of what the advert should look like already or a schematic diagram of the advert. You will then work from this brief. I will then supply you with a high res (300dpi) image and text (in a word document). I will also brief you on the size and font type of the text and the background colour. Therefore, the job will be to lay out each ad on the page according to the brief supplied. Once the print-ready pdf has been produced, it will be sent to me and I will send the proof to businesses for their approval. Part of the job will be to make up to one amendment per business (although hopefully there will be very few amendments!) The size of the booklet will vary each month, somewhere between around 32 and 64 pages. To give a specific example: in a 64 page booklet, let's assume we have: double page (14 adverts = 28 pages), single page (15 adverts = 15 pages), half page (14 adverts = 7 pages) and third of a page (27 adverts = 9 pages). That's a total of 59 pages of adverts. Please note, the double page spread contains 14x3 ads = 42 plus 14 ads, which is a total of 56 ads to lay out. Therefore, in this example, there would be a total of 56 + 15 + 14 + 27 = 112 ads to lay out. The booklet will also have an additional 5 pages for the front and back cover and the first page, which will be the contents. I would be grateful if you could let me know roughly how long it would take to lay out these 112 ads in an A5 landscape booklet as a print-ready pdf and roughly what you would charge for this job? I don’t expect there to be many amendments. But if there are say 10, what would this cost or could you add this to the price? Thanks, Clive