This thread is 9+ years old when BTC was MUCH easier - see the comment above: BTC was around $100 or less then.

Things are very different now.

As an example, I have a dual FutureBit system running (one full node and one standard) which averages a bit more than 6 gHash or (about) 6,000 mHash. That rig generates about 0.00017 BTC per week or about $5.00 USD. At current BTC prices that's a few cents more than the electricity it costs to run. A single FutureBit full node costs $899 for 3 gHash or about $0.30/ mHash. At this level it's basically a hobby with the hope that "stacking sats" will pay off sometime in the indefinite future.

Bottom line: DIY FPGA mining at that level is a lot of work for zero return.

All that said... if you enjoy DIY electronics (I build Eurorack synth modules "for fun", LOL) and are reasonably competent/confident with modern software development tools, building a small miner could be an interesting project. There are a number of reasonably recent videos on YouTube documenting such projects and you can find PCB layouts, software, etc. on github.

For example: https://www.youtube.com/watch?v=M_AocgfvTIs&t=290s

Good Luck!