Hello Rohini,
Unless you already have strong references (or relationships) in the Canadian investor community, it is extremely difficult to get a letter of support from investment groups. You should apply to incubators, but before that you need to ask yourself these questions:
1) Is your business in the tech (AI, AR/VR, marketplace, cleantech, biotech, additive manufacturing) industry? If yes, do you own the intellectual property rights and majority shareholding of the company?
2) Is a sizeable portion of your revenues being generated through North American customers? If not, is there a proof of concept which validates the need for your product/service in North America?
3) How familiar are you with Canadian business laws with respect to operating a company?
If your answer is 'No' for two or more questions, the Start-up visa route might not be the best approach.
There are a number of designated incubators and all of them have different focus sectors. For example, if you are into Cleantech and apply to a media-based incubator then that's not going to work. You have to pick an incubator which is a fit for your focus area and growth stage.
Some incubators take a share of your business. Others will ask for a minimum lease period in their office space. But regardless, there will be a due diligence process involved with long processing times. Most applicants will be required to make one or more visits to Canada before being accepted by any designated entity.
Incubators support your business through strong relationships with government and private sectors. For example, an incubator can help make connections with provincial Govt. resources for various grants and tax breaks. They can help get you connected with accounting/legal firms - this is particularly useful if you're new to a country.