Is building a house feasible with this equity and net income?

Additional costs do not belong in there. A 100 percent financing is when you finance the house and land without additional costs.
If you finance these as well, it is also called 110% financing.

To my knowledge, the ancillary construction costs are part of the production costs and thus part of the "100%". However, before the bank determines the lending value, it often deducts a flat rate (~15% safety margin).

The acquisition ancillary costs and everything else the builder still needs count as additional costs that are usually not financed. Depending on the property transfer tax, etc., this then adds up to 115% to 120%, and thus the equity capital melts away.