I will build custom desktop application

Only if you choose a cloud provider. I can also configure your app to use a local model (Ollama, LM Studio, or ONNX Runtime) so your data never leaves the user's machine — ideal for healthcare, legal, or regulated industries.

Both. I regularly work on legacy .NET Framework applications and can integrate AI into them. Modern .NET 8 makes some things easier, but it is not a requirement.

For the work itself, yes — I need an API key to test. I will never hardcode it into the source; it is always stored in a config file or Windows Credential Manager. After delivery, you use your own key.

Yes. I use IAsyncEnumerable and token-by-token streaming so the chat feels like ChatGPT — text appears as the model generates it, not in one big block at the end

It depends on the provider and model. OpenAI GPT-4o is around $2.50 per million input tokens and $10 per million output tokens. For your use case I can estimate monthly cost during our initial chat.

RAG is only in the Premium package because it requires embedding models, a vector store, and document ingestion pipelines — typically 3–4 extra days of work

Yes, always, before any code or design discussion

You do. I retain no rights to client-commissioned code.