Only to the extent of capital he personally puts at risk. Seller financing secured on the assets of the business being bought does not count as his investment, so a deal that is mostly seller-financed usually fails the substantiality test even if the headline price is large.
Only money he can lose counts
The treaty-investor rules ask whether the investor has placed his own capital in the enterprise such that it is subject to partial or total loss if the business fails. Indebtedness secured by the assets of the enterprise is excluded because if the garden centre collapses, the seller repossesses the inventory and the buyer walks away with a loss limited to his cash. What goes wrong is that buyers negotiate the commercial deal first and the visa second, then discover that the structure they agreed leaves a small qualifying investment relative to the purchase price.
The repair is to fund more of the price from personal sources: savings, proceeds of selling nursery equipment, or a loan secured on his Canadian home or land, which counts because he bears the risk personally. The investment must then be substantial in proportion to the total cost of the business and sufficient to ensure his commitment to its success. Consulates apply a proportionality view rather than a fixed dollar minimum, so a modest business bought mostly with personal funds can qualify where a larger one bought on seller credit does not.