IMO, best in digital is a DSLR equipped with a wide angle tilt and shift lens. Only such lenses I'm aware of are made by Canon and Nikon for their DSLRs (or film SLRs). Pros who do architecture or product shoots seem most likely to buy such lenses since they do top $2000 for a wide one. Conventional lenses as they get wider have ever increasing perspective issues. Lines curve easier in barrel fashion and things like walls and buildings seem to lean backward. Additionally, distance between objects appear farther and farther apart as a wider view is chosen. Computer image editing software can address the curving (barrel distortion) and the leaning so all is not lost. An entry level DSLR is where I would look first and usually they come with a kit zoom lens that is in the 18-55 mm focal length range. At 18mm it would give a view that can take in about 65 degrees horizontally. That is considered wide and if that is not enough a wider lens can be had. One I own is a Canon superwide 10-22mm lens ( $750 ) and it can take in a view that is up to nearly 97degrees wide
Interior shots with very wide angle lenses also create Lighting challanges. At the very least, a outboard and very powerful flash is needed to cover the angle of view that the lens sees. Even then, at 12mm or wider, I am not sure there are many flashes that provide the requisit coverage. Available light augmented with spot lighting is best. A flash will create a near/far problem (if you expose close, the distance will be dark, and vis versa).
So an important question for the OP is what kind of lighting was she anticipating?
More to the point would be to ask the size of the interior being photographed. Nothing mentioned gave a clue if it was a standard room with nice reflective walls or an interior the scale of the railroad museum roundhouse we both photographed. Then consider some venues don't allow flash let alone a flash setup. Color me ..unsure.