The capital of Vietnam is still far more traditional than the larger Saigon in the south. There aren’t a lot of must-see sites, but the pleasant (though chaotic) city center makes up for that, with excellent food and drink at very low prices.
Most of the cheaper hotels are right in the Old City, and more up-market hotels tend to be in the nicer suburbs to the south and west. Standards are higher than you might expect, and many places have free Wi-Fi in the lobby or even in all the rooms.
Attractions cost almost nothing by Western standards, so your sightseeing budget goes a long way. As long as you avoid an organized bus tour then you can get by on a tiny budget. The popular overnight trips to Halong Bay and multi-day trips to Sapa can range in price greatly, and often the cheap versions are great, though it’s always a bit of a crapshoot.
Local food is extremely cheap by most standards, with full meals in tourist restaurants usually costing between US$2 and 3, with cold beer adding around $1 each. Other alcohol is more expensive, but still cheap compared to most places.