I would like to offer a discounted rent rate for three months and then start charging the agreed rent amount. Would I be jeopardizing the agreed rent amount if I give this discount?

The Regulations of the Residential Tenancies Act set out different rules when providing discounted rents while protecting the lawful rent. You can review these rules under Regulations 516/06 sections 10 and 11 at https://www.ontario.ca/laws/regulation/060516. Further, you can review Part G entitled Rent Discounts from the Standard Form of Lease which discusses the legal ways of giving a rent discount. To review the Standard Lease, visit https://www.ontario.ca/page/guide-ontarios-standard-lease