You have asked a good question. While many experts have tackled the question from the area of what marketing research is, talking about the tools needed inconducting a viable market research, I would like to tackle the question from the area of data reliability. I am using this angle because of the meagre resources at your disposal.
It is indeed a cause for concern if you are sourcing for investors. You need to be able to convince them that you have done your due diligence but without money this might be easier said than done. You can go with the Google questionnaires and all but be sure that the data is very reliable, consistent and also recent. This will make your potential investors to see that the data source is good and the proposed venture is what they can embark upon. Use also your personally gathered data and make sure that the interpretation is too notch. If you have any further questions you can call me for more help.