buyer wants three months of transition support after the sale - how many hours is that really

On the money: it is common for a portion of the price to be held back and released when the transition milestones are met, either in escrow or by the marketplace if you are selling through one. Expect the buyer to ask for it and do not treat it as an insult.

What you want is for the release conditions to be objective and dated. Not their satisfaction, which is unfalsifiable. Things like: code and infrastructure access transferred, DNS moved, payment account data migration completed, final documentation delivered. Each with a date and a percentage attached.

Also agree who owns customer communication and when. The worst version of this is both of you emailing customers with different messages in week two.

The technical handover item that will eat your timeline is the payment side. You generally cannot hand someone your processor account, so the buyer needs their own, and moving stored card data between accounts is a documented but non-instant process that goes through the processor's migration team, with forms and approvals on both sides. Copies of modest size are typically completed within a day or two once approved, but there are eligibility rules - certain cross-region combinations are excluded and tokenised cards do not come across.

Start that paperwork the week you sign, not the week you plan to switch over. Everything else - repository, domain, DNS, third party keys - is an afternoon by comparison, and the subscription state is the thing that actually determines whether customers notice.

Reasonable assistance is the phrase that costs people their weekends. Replace it with numbers before you sign.

What I would put in: a cap in hours per month, a total cap across the period, response times measured in business days rather than hours, a defined channel so it is not text messages at 11pm, and a rate for anything beyond the cap. Something like eight hours a month for three months, up to twenty-four total, replies within two business days, everything in one shared thread, and an hourly rate after that.

The hourly rate is the important one. It is not there to earn money, it is there to make the buyer triage their own questions. Unlimited free support gets used carelessly. Metered support gets used precisely, and both sides end up happier.

Write the documentation before the transition period starts, not during it. Every question the buyer asks that is answered in a document you already wrote costs you five minutes instead of an hour of reconstructing your own reasoning.

Mine was about fourteen pages: architecture, deploy process, every scheduled job and what it does, the four support questions that make up most of the inbox, the customers who need special handling, and a list of things I would have fixed. That last section built more trust than anything else in the deal.

Three months is on the long side for a small tool. One month with a defined cap, plus a paid option to extend, is a cleaner structure and buyers accept it more often than you would expect. The length is usually anchoring rather than a real requirement.