@John Boby Good question. I'm guessing LLC but I'm not familiar with creating a business in Canada. I look forward to see what fellow experienced investors have to say.
I usually think about this situation in the other direction - Canadian purchasing in the U.S.A., but many of the concerns will be similar.
There is no single "best entity or entities" for a U.S.A. citizen to invest in Canada. How you choose to own/hold your Canadian properties will depend largely on your own personal situation and your objectives for owning property in Canada.
The best advise would be to find an attorney and accountant who specialize in cross-border business and real estate matters.
Some things to keep in-mind:
1) There is a tax treaty between Canada and the U.S.A. which provides favourable taxation on repatriated earnings from a U.S.A. company which is a 100% child entity of a Canadian corporation. I seem to recall similar terms in the other direction. You will want to read and understand the gist of the Canada - U.S.A. tax treaty.
2) If plan to acquire several properties in Canada, then it may be beneficial to form a holding company which you either own directly or in-directly through a U.S.A. entity. If you hold property directly, you will be forced to repatriate all earnings (minus the withholding) on an annual basis {from an income tax perspective}. If you hold the properties in a Canadian company, the company will pay taxes in Canada (at the top marginal tax rate since the income is deemed to be passive) and you can choose if and when you repatriate any retained earnings.
Canada does not have LLCs, so your choices would be a sole proprietor (own the properties in your own name) or a corporation.
3) Whether you own a Canadian company directly or as a 100% child entity of a U.S.A. company would be a matter decided by you and your accountant.