Fairly open access to a large market.
And they require that in exchange, the Ukrainians do unthinkable and abominable things--human rights/democracy, fight corruption, strengthen the rule of law. And even reform the economy (which right now is a problem, to be honest: even as the "Dombass" (as so many signs have read ... truly, the "dvoechnye" are in charge) is falling to pieces and coal is likely to become less important the government is increasing wages to the miners.
Ukraine is one of the least reconstructed Soviet spaces left. And it shows. So until very recently the "internal defense forces" were fighting, having borrowed some troops from the army. But they were fighting under "anti-terrorism" laws. It's like having the National Guard in the US be part of the FBI. And the whole gorsoviet, oblsoviet, structure ....
It's not by coincidence that this is so. Early on the Communist Party (which is, oddly, one of the more "fascist" groups) had a lot of power. And it's not a coincidence that the Communist Party in Ukraine is out-represented in the ranks of the LPR and DPR membership and leadership, in supporting them from elsewhere in Ukr, or that the Russian Communist Party is supporting the LPR and DPR. (Same for Georgia, where the CP is really pro-Russian and pro-Putin. They're one of the outposts of Russian ultranationalism and irredentism.) It's not surprising that the Russians Zhirinovsky, Limonov, and Zyuganov--two fascists and a communist--pull in unison in rowing this particular boat.
Still, the recent attack by the Pravsek and some other nationalist group on the "soviet" of the worker's unions today is uncalled for. (They should save their ire for Tsaryov.)