i've a site in which a product is available for subscription and plans are 1 month, 3 month, 6 month, 12 month and price is vary according to plan. notify the user before 2 day of expiring of subscription
I hate to offer an answer that isn't too much more than a link, but well the question itself is very weak and most importantly there's little incentive to build this yourself when it already exists as a plugin:
You could either create different products for each of the subscription plans, or now it does support variable subscriptions.. so you could just do the different monthly plans as a variation of the same produce.
The only thing I couldn't vouch for would be the expiration warnings. Otherwise it is a really good plugin.... and you would definitely spend more than $99 hiring someone else to do it or in time to figure it out yourself.