Questions about buying a lot for a custom build

Hello! I'm in Guelph, have always loved the idea of a custom build, but don't have a massive budget. Have heard that a 50x150 building lot may come up in my older and saturated neighbourhood that interests me greatly!

What is the best way to figure out if the lot is worth purchasing and figuring out how much money would be needed to make it ready to build? I can look up City of Guelph servicing fees online, but I'd love someone to visit it with me and make sure that a 2500-2700 sq ft house is manageable meeting all bylaws/codes etc. There's also 3 or 4 mature trees that would need to come down, and the lot has about a foot or two of elevation change from side to side. I have done a lot of reading, but I sure there are a tonne of intricacies I'm still unaware about.

My thought would be an architect, but perhaps I need a builder or a surveryor? Would love to hear some advice. It would be also nice to have someone who could also roughly estimate what my grand idea would cost, so I don't buy land and realized I'm 250k off on my budget.

Thanks for your help.